It's because onions really form the bedrock of our cooking. ... Cooked onions give dishes a rich umami flavor and a subtle sweetness — you don't always know onions are there once the dish has been spiced and sauced, but you'd definitely miss them.

Do onions add flavor to food?

Onions add texture and flavor to foods, either complementing it as the base of a soup, a rice or noodle dish, or whether they are used as a main ingredient. Onions can have a spicy perk-me-up taste if eaten raw in a salad, or they may be very soft and sweet when caramelized and have turned a beautiful golden brown.

Why do onions add flavor?

Amino acids are the building blocks of proteins. Cysteine is one of just a few amino acids that contain the element sulfur. Methionine is another one. Thus all of the compounds responsible for the aroma, flavor, and tearing effect of onions contain the element sulfur incorporated into their chemical structure.