Peel and chop 1 large red onion in half, then cut it into thin slices.Pinch it with your fingers to separate its layers.
Add to a bowl or jar and cover with ½ cup white vinegar, the juice of 1 lemon, and 1 teaspoon salt.Optionally you can add 2 teaspoons sugar, 1 pinch red pepper flakes, and a spice of choice (we suggest sumac).
Stir, mix, and press down the onions in the liquid.Set them aside at room temperature for 30 minutes or until they have softened up, lost their sharpness, and acquired a bright fuchsia color and tangy taste.