In large saucepan, cook ground beef and onion over medium heat until beef is thoroughly cooked, stirring frequently. Drain. Add chili beans and tomatoes; cook 2 minutes or until thoroughly heated, stirring occasionally. Add hot pepper Monterey Jack cheese and 1/2 cup of the Cheddar cheese; mix well. Spoon evenly into spaghetti-lined pie pan. Top with remaining 1/2 cup Cheddar cheese.