Caramelized onions are onions that have been slowly cooked over low heat until they become soft, sweet, and golden brown. This process typically takes about 30 to 45 minutes and involves the natural sugars in the onions breaking down, enhancing their flavor. Common types of onions used for caramelization include yellow onions, sweet onions, and red onions. These flavorful onions are often used as a topping for various dishes, such as burgers, pizzas, and sandwiches. They can also be incorporated into sauces, soups, and casseroles, adding depth and richness to the overall taste. Caramelized onions are a versatile ingredient in many cuisines.