In this step-by-step guide, I'll teach you how to make the best caramelized onions with a few simple ingredients.
Caramelized onions have a rich and deep flavor with sweet and sour notes. They are soft and literally melt in your mouth.
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What to expect
This is an essential technique for any home cook as caramelized onions come in handy for starters, dips, soups, salads, pastas, burgers, and most kinds of sandwiches really.
By the end of this article, you'll know exactly what the best onions are, how long it takes, and which pan to use. Plus, I'll share my personal tips on how to make them perfect every time.
Caramelized onions are onions that are cooked slowly, over medium to low heat, until they become soft and caramelized.
The onions become so soft that they will melt in your mouth. The pungent taste of the onion is all gone, and all your left is a concentrated, rich, umami-packed, and sweet taste.
The first, and most important secret about caramelized onions is time. Yes, it takes about 45 minutes to make the best caramelized onions. However, they will only require about 5 minutes of your attention as they can simmer patiently on their own.
So don't try to shorten the cooking time by for example turning the heat too high or you'll surely end up with burnt, charred onions.
The best advice I can give you is to make this recipe in advance, not right before you need it, but a day or two in advance.
Do it after dinner, while sipping on a glass of wine, maybe with some lounge music on, tending to the onions occasionally to make sure that they are doing fine.
Ingredients and Substitutions
- Onions: you can caramelize any kind of onions. White onions, yellow, red, shallots, and sweet onions. We usually caramelize yellow and red onions.
- Fat: some like to use butter but we prefer to use extra virgin olive oil as it seems to be associated with longevity as opposed to butter.
Also, extra virgin olive oil not only gives great flavor to the onions, but research shows that it is the best oil for cooking thanks to the high amount of antioxidants.
Antioxidants protect the oil and give it great oxidative stability, which basically means that the oil won't become toxic when exposed to heat for a long time. That's only true for extra virgin olive oil, not refined olive oil.
- Water: we add water to help the onions get soft and to prevent them from burning. Adding water makes it easier to make caramelized onions. The water evaporates completely, so don't worry, you won't get watery caramelized onions.
- Salt: to add flavor. The onions will be bland without salt.
- Sugar: add a little sugar to help the onions caramelize. They will be a lot more flavorful this way.
- Vinegar: this is our secret ingredient to make the best caramelized onions really. Vinegar adds a touch of acidity and sweetness to the onions. It elevates their flavour wonderfully. We recommend balsamic vinegar if you are using red onions, and apple cider vinegar if you are using white or yellow onions.
How to make caramelized onions
Cut the onions
As a first step, peel your onions and cut them into slices. You can either cut your onions in half first, then slice them, or you can slice the onion into thin onion rings.
In either case, don't slice them too thin or too thick. Try to aim for ⅕ inch or ½ cm.
I prefer slicing the onions into onion rings as I think the caramelized onions look nicer this way. Try to cut even slices so that the onions cook evenly
Pan fry for 5 minutes
To a nonstick pan with a heavy bottom add the extra virgin olive oil, then add the onions on top.
Season with sugar and salt, and fry on medium heat for about 5 minutes, stirring occasionally and separating the onion layers.
You can definitely do caramelized onions without the sugar, just caramelizing the natural sugars of the onions. But with a little help from the sugar, the flavor of these onions is going to be unbeatable.
Also, this first step of frying the onions in oil helps build flavor.
Simmer for 40 minutes
Then when the onions are soft and translucent you can add the water and set the heat to medium-low.
Let the onions simmer on a gentle heat for about 40 minutes. I'd recommend setting a timer. Just remember to check the onions occasionally, every 10 minutes or so, to give them a quick stir.
After 40 minutes your onions should be very soft and the water is completely gone. The pan should be hot and dry, but the onions are still very moist.
Add a splash of vinegar
At this point, turn the heat to medium-high, add a splash of vinegar to the hot pan.
Stir the onions constantly for about 2 to 3 minutes to mix them with the vinegar. The pan is hot at this stage so stir the whole time.
Use apple cider vinegar for white and yellow onions, balsamic vinegar for red onions.
If the onions stick to the pan but 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.
The vinegar serves to deglaze the pan, it adds acidity, and it really brings this recipe together by boosting the flavor of the caramelized onions.
Try tasting the onions before and after adding the vinegar to see what a huge difference it makes.
Then when the vinegar has evaporated completely, turn the heat off, taste the onions and add a pinch of salt if necessary. Your caramelized onions are ready!
If you used white or yellow onions, once they are caramelized they should have a deep golden brown color. If you used red onions, they should be very shiny and of a dark purple color.
If you are wondering how to use caramelized onions, just know that this caramelized onion recipe is essential for any home cook as they come in handy for starters, dips, on pizza, in soups, salads, pastas, frittatas, socca, burgers, and in most kinds of sandwiches really.
Put the onions on our flatbread pizza with avocado and chipotle sauce, with focaccia bread, or even on top of tofu scramble on toast.
Serve them with our tomato confit and vegan ricotta to make your starters unique, for example, try them on bruschetta with tofu cream cheese, with white bean dip, or on top of our mini pizzas.
They are so versatile that you can use them in most savory dishes, from french onion soup to most everyday easy dinners.
You can even make a caramelized onion dip mixing the onions with a couple of tablespoons of dairy-free yogurt and a couple of tablespoons of dairy-free cream cheese or of vegan mayo.
What's the best pan for caramelizing onions?
You'll need a good large skillet with a heavy bottom. "Heavy bottom" simply means that your pan has a thick bottom 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.
When it comes to materials, you could use a cast-iron skillet, however, if you do, make sure it's well seasoned and you know how to cook with it. It's really 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 nonstick pan or sauté pan, ideally with a heavy bottom.
Stainless steel pans work too, provided that they also are of good quality and with a thick heavy bottom. But they require a little more hands-on to prevent the onions from sticking to the pan.
Keep caramelized onions in the fridge for up to 1 week, ideally in a small jar.
You can freeze caramelized onions for up to 3 months in a freezer-safe container for up to 3 months. However, I'd recommend freezing them in icecube trays, then when they are solidly frozen, take them out of the tray and transfer them into a freezer-safe bag.
With this trick, you can just thaw the onions you need, without defrosting the whole batch.
Caramelized Onions Recipe
- Non-stick pan best if with heavy bottom (11 to 12 inch or 28 - 30 cm)
- 4 medium onions white, yellow, or red
- 1 tablespoon olive oil extra virgin
- 1 tablespoon sugar
- 1 teaspoon salt
- 1 cup water
- 1 tablespoon vinegar apple cider or balsamic vinegar
- Slice the onions. You can cut them in half first and then slice them, or you can slice them into onion rings.In either case, don't slice them too thin nor too thick. Try to aim for ⅕ inch or ½ cm.
- To a large non-stick pan add the olive oil, sliced onions, salt, and sugar.Sauté the onions on medium heat for 5 minutes, stirring often and separating the onion layers.
- Add the water and turn the heat to medium low. Let simmer gently for 40 minutes till the onions are completely soft and shiny, and the water has evaporated.Stir occasionally during this time so that the onions cook evenly and don't stick to the pan.
- Turn the heat to medium-high, then when the pan is hot deglaze with (add) the vinegar.Stir constantly for 3 minutes to mix the onions with the vinegar, scraping all the brown bits from the pan. When the vinegar has completely evaporated your caramelized onions are done.Taste and adjust for salt before serving.
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