Tuscan onion soup baked with bread and Parmigiano is vegetarian comfort in a bowl. This mediterranean family dish is fresh, healthy, and a warm, satisfying dinner for cool evenings.
Peel and slice the onions thinly. In a large heavy pot, heat olive oil over low-medium heat until shimmering, then add the onions.
Cook onions slowly for 25-30 minutes, stirring often, until deeply golden and caramelized, adjusting heat as needed to prevent burning.
Pour in the vegetable broth, add thyme, salt, and pepper, and bring to a gentle simmer. Let the soup cook uncovered for 15 minutes to meld the flavors.
While the soup simmers, toast the bread slices in the oven at 400°F until crisp and golden, about 8 minutes per side.
Ladle the soup into oven-safe bowls, top with toasted bread slices, sprinkle Parmigiano generously over the top, and broil on high for 2-3 minutes until the cheese is bubbling and lightly browned.