In a large bowl, combine the beef, onion, 1/2 cup tomato sauce, bread crumbs, salt and pepper. Press into a greased 8-in. square baking dish.
In another large bowl, combine the rice, cheese and remaining tomato sauce. Pour over meat mixture. Cover and bake at 350° for 25 minutes. Uncover; bake 10-15 minutes longer or until rice is tender. Let stand for 5 minutes before cutting.