cook macaroni according to package directions, drain. Stir in 1/3 parmesan, the 1/4 cup milk and 1 egg, set aside.
In skillet cook ground beef and chopped onion until meat is slightly brown and onion is tender; drain off excess fat. Stir in tomato sauce, the 3/4 teaspoon salt, the cinnamon, nutmeg, and pepper, set aside
In a saucepan melt butter; blend in flour and the 1/4 teaspoon salt. Stir in the 1 1/2 cups milk; cook and stir until thickened and bubbly. Cook and stir for one minute more. Stir only half of the sauce into 1 beaten egg, return that back into the saucepan. Stir in the 1/4 parmesan cheese.
Layer half of the macaroni mixture in a 8x8x2 inch baking pan. Spoon meat mixture atop, then remaining macaroni. Spread cream sauce over all. Bake, uncovered at 350 degrees for 45-50 mins. Let stand 10 minutes before serving.