Cook the spaghetti and set aside. Put butter in a pan and chopper onions and let the onions get brown. Mixt the flour in a glass of milk. Pour the mixture in the pan and add the other glass of milk and the tomato sauce. Let until it is cooked, add salt, pepper, and the tuna. Add the sour cream (0.70 pounds). Get a retangular container and put sauce at the bottom. Put spaghetti, some slices of ham, some slices of cheese. More spaghetti, the sauce, ham and cheese at the top and put the sauce. Sprinkle with apated cheese, put small pieces of butter. Take to oven and cook until cheese melt.