Preheat oven to 350º Place half of  the cooked spaghetti in a lightly buttered 13 x 9 inch baking dish. Sprinkle with half the of cheese. Repeat layers. Combine flour, salt, pepper, and dry mustard in a small bowl, whisk in 1 tablespoon milk. Add remaining milk and eggs to flour mixture, stirring with a wire whisk until blended. Pour milk mixture over spaghetti mixture. Dot with butter.

Bake at 350º for 45 minutes or until set. Let stand 5 minutes before serving.

Serve with garden fresh, sliced tomatoes.