Frittata al formaggio or cheese frittata is a traditional dish and probably the most commonly made type of frittata in the country. It's often made with a combination of eggs, butter, salt, pepper, and cheese such as Parmigiano-Reggiano and Emmentaler.
The eggs are whisked, seasoned with salt and pepper, then beaten with the addition of grated cheese. Once the butter in the pan has started to foam, the egg mixture is poured into the pan and cooked over low heat until the eggs set and the top is still runny.