Add 2 cups milk; cook and still till thick and bubbly. Add 1/4 cup finely chopped onion and 8 ounces cheddar cheese or mixed cheeses, cubed. (This is the secret... we use only really good flavorful cheeses). Stir till melted.
Mix cheese sauce with macaroni. Turn into 1 1/2 quart casserole. Sprinkle 1 sliced tomato with salt; arrange on top. Bake at 350° for 35 to 40 minutes or until heated through. Makes 4 servings.
We triple this recipe and put in a long baking dish. You can spice this up if you wish with red pepper and more onions.)