Caramelized onions have a rich and harmonious sweet taste and a complex flavor profile with hints of tangy, savory, and earthy notes.

Here, we’ll show you how to make caramelized onions in one skillet with 6 simple ingredients and how to use them to elevate any dish.

Try them on spreads, salads, bowls, burgers, sandwiches, pasta, pizza, and rice dishes. They are your secret ingredient to elevate any dish.

Caramelized onions on a white platter

Dietary Note: this recipe is suitable for a vegetarian, vegan, and gluten-free diet.

Caramelized onions are cooked slowly over medium to low heat until their natural sugars caramelize, and the onions develop a golden-brown color, a soft texture, and a bold, sweet, and savory flavor.

Make them in advance and keep them in the fridge, ready for use on your favorite dishes.

You’ll need about 30 to 45 minutes to cook them slowly; the good news is that they require almost no attention as they can simmer patiently on their own.

Caramelized onions on lentils and rice served on a white plate

Caramelized onions video

Ingredients & Substitutions

Ingredients onions and vinegar

Quantities are in the recipe box at the bottom of the page.

Onions

You can caramelize any onion: white onions, yellow onions, red onions, shallots, sweet onions, or Vidalia onions.

We usually caramelize yellow and red onions.

Olive Oil

We use extra virgin olive oil as research shows it is the best oil for cooking thanks to the high amount of polyphenols that keep it stable at high temperatures.

Polyphenols protect the oil and give it excellent oxidative stability, which means it won’t become toxic when exposed to heat for a long time.

Substitute avocado oil or another vegetable oil for extra virgin olive oil. Some use butter to caramelize onions.

Water

We add water to help the onions get soft and to prevent them from burning.

The water evaporates completely, so don’t worry; you won’t get watery caramelized onions.

Salt

Use sea salt or kosher salt to add flavor. The onions will be bland without salt. A twist of black pepper is optional.

Sugar

Add some white or brown sugar to help the onions caramelize. The sugar will bring out the onions’ natural sweetness, making them irresistible.

You can caramelize onions without sugar. They will take longer and will be less sweet.

Vinegar

This is our secret ingredient to make the best caramelized onions. Vinegar adds a touch of acidity to balance out the sweetness of the onions.

It elevates their flavor wonderfully. We recommend balsamic vinegar if you use red onions and apple cider vinegar if you use white or yellow onions. Any other vinegar works well, too.

caramelized onions on hummus

How to make caramelized onions

US cups + grams measurements in the recipe box at the bottom of the page.

Cut the onions

Cut the onions in half, peel them, and cut them into ⅕ inch or ½ cm slices.

Tip: to reduce the crying-inducing effect of the onions, cut them in half, peel them, then rinse them under cold water. Cutting them with a sharp knife also helps.

slice onions

Pan fry for 5 minutes

Heat the extra virgin olive oil in a large skillet with a heavy bottom. Add the chopped onions, sugar, and salt and fry on medium-high heat for 5 minutes.

Stir to separate the onion layers.

Tip: This first step of frying the onions in oil helps build flavor.

onions with sugar

Tip: It’s best to use a heavy-bottom skillet or Dutch oven. We like to use a large enameled cast-iron skillet. You can also use a Dutch oven, a nonstick pan, a stainless steel pan, or a well-seasoned cast iron skillet as long as they have a heavy bottom.

Tip: You can make caramelized onions without the sugar; just caramelize the natural sugars of the onions. But with a bit of help from the sugar, the flavor of the onions will be unbeatable.

Let the onions cook slowly

When the onions are soft and translucent, add the water and simmer on medium-low heat for 30 to 40 minutes.

I’d recommend setting a timer. Then, check the onions occasionally, every 10 minutes or so, to give them a quick stir.

After 30 to 40 minutes, your onions should be soft, and the water should be gone. The pan should be hot and dry.

Tip: if you double our recipe or increase the onions, you’ll need more than 40 minutes. As the pan gets crowded, the caramelization process slows down.

caramelized onions at different stages

Add a splash of vinegar

Then, turn the heat to medium-high and add vinegar to the hot pan.

Stir the onions constantly for 3 minutes to mix them with the vinegar. The pan is hot at this stage, so stir it the whole time.

Then, when the vinegar has evaporated completely, turn the heat off, taste the onions, and add a pinch of salt if necessary.

Tip: use apple cider vinegar for white and yellow onions and balsamic vinegar for red onions.

Tip: the vinegar serves to deglaze the pan, adds acidity, and brings this recipe together by boosting the tangy and savory flavors of the caramelized onions.

If the onions stick to the pan, that’s fine. Keep stirring with a wooden spoon and scrape all browned bits from the pan, but make sure the onions don’t start burning.

brown onions

Serving Suggestions

You can use caramelized onions as your secret ingredient to boost the flavor of many dishes, including appetizers, mains, and side dishes.

caramelized onions on a platter

Caramelized onions as an appetizer

Use them to top small plates, tapas, or toasted bread. Some of our favorite ideas are:

Caramelized onion hummus

Caramelized onions to enhance a main dish

Arrange them on a small serving plate and put them at the center of the table so that your guests can add them to their plates.

Or use them to enhance the flavor of other recipes. Try them:

You can even make a caramelized onion dip by mixing the onions with a couple of tablespoons of yogurt and a couple of tablespoons of cream cheese or vegan mayo.

Mujadara with caramelized onions and lemon wedges

Variations

Caramelized red onions

To caramelize red onions, you can follow the same process as above.

The result is very similar. While white or yellow onions have a deep golden brown color, red onions should be very shiny and dark purple, almost black.

Red caramelized onions

Tip

What’s the best pan for caramelizing onions?

You’ll need a large skillet with a heavy bottom. “Heavy bottom” means that your pan has a thick base, which will distribute the heat more evenly.

If your pan has a thin bottom, the onions will stick to the bottom of the pan very quickly.

Regarding materials, you could use a cast-iron skillet; however, if you do, ensure it’s well-seasoned and you know how to cook with it.

It’s easy to burn things on a cast-iron skillet and fill your kitchen with smoke if you are not used to cooking on it.

We prefer using (and we recommend using) a good-quality enameled cast-iron skillet or a good-quality nonstick pan or sauté pan with a heavy bottom.

Stainless steel pans work, too, provided they are of good quality and have a thick, heavy bottom.

But they require a little more hands-on to prevent the onions from sticking to the pan.

Questions

Are caramelized onions sweet?

Caramelized onions are a savory food with sweet notes due to the caramelization process that transforms the hidden natural sugars (sucrose) in the onions into a simpler sugar that our tongues can taste (glucose and fructose).

Also, some caramelized onion recipes contain a little added sugar to enhance the sweet flavor of this delicious dish.

The best caramelized onions are a perfect balance of sweet and acidic flavors that make them irresistible to our taste buds. The sour flavor is often added through apple cider vinegar or balsamic vinegar.

Do you need to add sugar to caramelize onions?

You don’t need to add sugar to caramelize onions. However, adding a little sugar – 1 teaspoon to 1 tablespoon – helps speed up caramelization.

Sugar also enhances the onions’ natural sweetness, making them more flavorful overall.

What is the trick to caramelizing onions?

Some tips to make the best caramelized onions are:

1) Cook them on a good quality skillet with a heavy bottom.
2) Add a little sugar to help the caramelization process.
3) Give them enough time to caramelize at low heat – at least about 40 minutes.

Do you caramelize onions with butter or oil?

Both unsalted butter and oil are suitable for caramelizing onions.

We recommend using extra virgin olive oil because, compared to butter, it is heart-healthy and stable at high and prolonged cooking temperatures thanks to the high amount of polyphenols.

Do you salt caramelized onions?

Yes, absolutely. You should salt caramelized onions to enhance their sweet, savory, and earthy flavor.

Storage & Make Ahead

Make ahead: caramelized onions are an excellent recipe to make in advance or for meal prep as they keep for days in the fridge.

Refrigerator: keep them in an airtight container in the fridge for up to 1 week.

Freezer: Let the onions cool down completely, transfer them to a freezer-friendly container, and freeze them for up to 3 months.

You can also freeze them in ice cube trays, then when they are solidly frozen, take them out of the tray and transfer them into a freezer-safe bag.

This trick lets you thaw the onions in small portions without defrosting the whole batch.

Thaw: Defrost them in the refrigerator for several hours. Serve at room temperature.

More Appetizers

Here are some more appetizers to pair with your caramelized onions:

More recipes with onion

Caramelized onions with a silver fork

Caramelized Onions

By: Nico Pallotta
5 from 8 votes
Caramelized onions have a rich and harmonious sweet taste and a complex flavor profile with hints of tangy, savory, and earthy notes.
Here, we’ll show you how to make caramelized onions in one skillet with 6 simple ingredients and how to use them to elevate any dish.
Prep Time: 10 minutes
Cook Time: 40 minutes
Total Time: 50 minutes
Servings: 10 people
Course: How tos, Starter
Cuisine: International

Equipment

  • Large skillet (11 to 12 inches or 28 – 30 cm) best if with heavy bottom. You can use enameled cast iron, nonstick, stainless steel, and well-seasoned cast iron.

Ingredients

  • 4 large onions white, yellow, or red (just over 1 pound)
  • 1 tablespoon extra virgin olive oil
  • 1 tablespoon sugar
  • 1 teaspoon salt
  • 1 cup water
  • 1 tablespoon vinegar apple cider or balsamic vinegar

Instructions 

  • Cut 4 large onions in half, peel them, and cut them into ⅕ inch or ½ cm slices.
    slice onions
  • Heat 1 tablespoon extra virgin olive oil in a large skillet.
    Add the chopped onions, 1 tablespoon sugar, and 1 teaspoon salt and cook on medium-high heat for 5 minutes.
    Stir often.
    onions with sugar
  • Add 1 cup water and simmer on medium-low heat for 30 to 40 minutes or until the onions are soft and shiny and the water has evaporated.
    Stir occasionally.
    caramelized onions in a skillet after 45 minutes
  • Turn the heat to medium-high and add 1 tablespoon vinegar.
    Stir for 3 final minutes, scraping all the brown bits from the pan.
    brown onions
  • Taste and adjust for salt before serving.
    caramelized onions on a platter

Video

Caramelized onions (40 mins)

Notes

Nutrition information is an estimate for 1 serving of caramelized onions out of 10 servings.
STORAGE & MAKE AHEAD
Make ahead: caramelized onions are an excellent recipe to make in advance or for meal prep as they keep for days in the fridge.
Refrigerator: keep them in an airtight container in the fridge for up to 1 week.
Freezer: Let the onions cool down completely, transfer them to a freezer-friendly container, and freeze them for up to 3 months.
You can also freeze them in ice cube trays, then when they are solidly frozen, take them out of the tray and transfer them into a freezer-safe bag.
This trick lets you thaw the onions in small portions without defrosting the whole batch.
Thaw: Defrost them in the refrigerator for several hours. Serve at room temperature.
ALSO ON THIS PAGE

Nutrition

Calories: 37kcal, Carbohydrates: 6g, Protein: 1g, Fat: 1g, Saturated Fat: 0.2g, Polyunsaturated Fat: 0.2g, Monounsaturated Fat: 1g, Trans Fat: 0g, Cholesterol: 0mg, Potassium: 73mg, Dietary Fiber: 1g, Sugar: 3g, Vitamin A: 1IU, Vitamin B6: 0.1mg, Vitamin C: 4mg, Vitamin E: 0.2mg, Vitamin K: 1µg, Calcium: 13mg, Folate: 10µg, Iron: 0.1mg, Manganese: 0.1mg, Magnesium: 5mg, Zinc: 0.1mg
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Nico and Louise in the kitchen

Hi! We are Nico & Louise

Welcome to The Plant-Based School, a food blog with easy, tasty, and wholesome recipes.

Our aim is to help you and your family eat more veggies through delicious recipes with simple ingredients.

Easy right?

5 from 8 votes (7 ratings without comment)

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2 Comments

  1. 5 stars
    I tried this very nice and simple recipe, using red onions together with the tomatoes confit. Delicious. I used them both as a side dish to a hot mean. The onions are easy to cook and you can leave them to simmer by themselves. Thanks Nico for another lovely recipe.