Depending on the recipe, white, red, yellow, or sweet onions can be used in French onion soup. However, ordinary yellow onions are the greatest choice for the tastiest bowl.

Yellow onions have a high starch content, which allows them to caramelize quickly, bringing

out the root's sugars without breaking down into mush.

When using yellow onions, there's no need to take the extra step of adding baking soda to adjust the pH or adding a pinch of sugar

to help in the caramelization.