. In a large saucpan, melt butter or margarine. Stir in flour. Stir in undrained tomatoes, your choice of sauce, onion or onion powder, water, and pepper. (If using tomato sauce or pizza sauce, add 1/2 teaspoon dried oregano, crushed.) Cook and stir till mixture is thickened and bubbly. Stir in your choice of meat and pasta. Turn into a 2-quart casserole. Bake, uncovered, in a 350F oven for 20 minutes. Sprinkle your choice of cheese atop. Bake 5 minutes more or till cheese melts.