French onion soup is a rich and flavorful dish that is perfect for showcasing the sweetness of caramelized onions. The onions are slowly cooked until they are golden brown and caramelized, which brings out their natural sweetness. The soup is then topped with a slice of toasted bread and melted cheese, which adds a deliciously gooey and savory element. The combination of the sweet onions, rich broth, and melted cheese creates a truly indulgent and satisfying soup.