In a large skillet, brown ground chuck with diced onion; drain grease. Add rice, tomatoes, soup, and spices. Add one soup can of milk if desired. Simmer about 10 minutes, stirring occasionally, until rice is done.
Spoon about 1/2 of the mixture into a 9x13 microwave safe casserole dish. Cover completely with cheese slices. Spoon in rest of mixture, cover completely with cheese slices.
Microwave about 5 minutes until cheese is melted. Serve.