Lasagna is typically finished with grated cheese before it is baked.
The cheese forms a savory topping that melts in the oven and can develop a browned, lightly crisp surface. In the classic northern Italian lasagne alla bolognese, grated Parmesan is layered with ragù and béchamel. Other regional and international versions may use cheeses such as mozzarella, ricotta, pecorino, or mixtures of several kinds.
Cheese is not merely a decorative final layer. It contributes salt, fat, aroma, and proteins that help unify the sauce and pasta as the dish heats. The exact cheese depends on the recipe and region, so “cheese” is the broad canonical answer rather than one specific variety.
Lasagna’s regional diversity is especially visible in Naples, where lasagne di Carnevale may include ricotta and mozzarella, sausage, meatballs, eggs, and Neapolitan ragù. Northern recipes more often feature béchamel, while Italian-American versions commonly adapt the balance of ricotta, mozzarella, and tomato-based meat sauce.
The finished casserole is assembled from cooked or partly cooked pasta and fillings, topped with grated cheese, and baked al forno.