Cook ground beef until browned, stirring to crumble. Drain off and wash with hot water. Stir in tomato sauce. Simmer the mixture about 20 minutes, stirring occasionally. Cook macaroni according to package directions, drain and set aside. Combine cream cheese, cottage cheese, sour cream, and onion, stir well. Layer half each of macaroni, cottage cheese mixture, mozzarella cheese, and meat sauce in a lightly greased 13 x 9 inch baking dish. Repeat layer except for mozzarella cheese. Bake at 350 degrees for 15 to 20 minutes. Place remaining mozzarella cheese on top. Bake an additional 10 minutes or until cheese melts.