"Onions, one of the oldest vegetables, are found in a large number of recipes and preparations spanning almost the totality of the world's cultures. They are now available in fresh, frozen, canned, caramelized, pickled, powdered, chopped, and dehydrated forms. Onions can be used, usually chopped or sliced, in almost every type of food, including cooked foods and fresh salads and as a spicy garnish. They are rarely eaten on their own, but usually act as accompaniment to the main course. Depending on the variety, an onion can be sharp, spicy, tangy and pungent or mild and sweet."~~~Wikipeda
Caramelizing onions, by slowly cooking them in a little olive oil until they are richly browned, is a wonderful way to pull flavor out of the simplest of ingredients. Onions are naturally sweet; and as caramel comes from the simple cooking of sugar, when you slowly cook onions over an extended period of time, the natural sugars in the onions caramelize, making the result intensely and wonderfully flavorful.