Slow cooking over low heat brings out tender, nutty sweetness in many vegetables. Some folks add sugar but I usually prefer to let vegetable flavors speak for themselves. A classic for caramelizing is the onion - here's the basic method.
2-3 TB olive oil
1 large onion, thinly sliced
Heat the oil in a skillet over low heat and saute the onions, stirring occasionally, for 15-20 minutes or until they are golden and soft.
Caramelized onions are one of the best toppings in the world for pizza.
Served up by Tod Dimmick,
AKA "The Foodie" at 1000radishes