For the pasta, cook macaroni until just done, drain. Add one beaten egg, 1/3 cup parmesan cheese and 1/4 cup milk. Mix and set aside.
For the meat sauce, cook the meat and onion in a skillet until the meat is brown, drain off the fat. Add tomato sauce, cinnamon, nutmeg, and salt and pepper to taste. Set aside.
For the sauce, melt the butter or margarine in a saucepan. Add in flour and 1/4 teaspoon salt. Add the milk slowly and cook and stir until thickened. Remove from heat and stir a small amount of the hot mixture into one beaten egg, return that mixture to the rest of the sauce in the pan. Add the 1/4 cup of parmesan cheese.
To assemble, put half the macaroni into an 8 x 8 inch square pan. Add the meat sauce next, then the rest of the macaroni on top of that. Add the sauce over all. Bake at 350 degrees for 40-45 minutes. Let stand 10 minutes before serving.