Place ground beef and onion in a large, deep skillet. Cook over medium high heat until evenly brown. Drain excess fat. Stir in water and rice. Season with beef bouillon and black pepper. Simmer 25 to 30 minutes, or until water is absorbed. Stir in diced tomatoes and green peppers. Simmer another 10 minutes, until green pepper is tender. Sprinkle top with cheese.