Carabaccia is the original onion soup originating from Tuscany. It dates back to the Renaissance, was Leonardo DaVinci's favorite, and consists of thinly sliced red onions, ground almonds for thickening, cinnamon, salt, pepper, olive oil, toasted bread, vegetable stock, grated cheese such as Pecorino or Parmigiano-Reggiano, wine vinegar, and either honey or sugar to bring out its sweet and sour flavors.
This ancient soup is a classic cucina povera dish that was made out of necessity.