Cook noodles as directed on package. Rinse well, set aside. Saute 1/4 cup onion with butter in large skillet until tender. Add beef and cook until lightly browned. Drain well, add tomato sauce, salt and pepper. Stir well; simmer for 20 minutes. Combine cottage cheese, sour cream and remaining onion. Stir well, set aside. Place noodles in lightly buttered casserole dish. Spoon cottage cheese mixture over noodles. Spoon meat mixture over that. Sprinkle with shredded Cheddar. Bake at 350 degrees for 25 minutes. Note: for a tasty variation, substitute Swiss Valley Farms shredded Swiss cheese for the Cheddar.