Combine the pasta, eggs and cheese, stirring well. Season.
Heat half of the butter in a large heavy bottomed frying pan. Pour in the egg mixture, lower the heat and cook for 10 minutes until the eggs are just set but still very soft. Slip a knife around the edge to loosen the omelet, then using a spatula turn the frittata cooked side up on to a plate (patch up the pieces if it breaks).
Heat the rest of the butter in the pan, slide the frittata back into the pan, soft side down and cook for a few minutes. You can also cook the top side by just dotting with butter and grilling, but I prefer the pan method.