cook macaroni. cook and stir butter onion salt pepper over medium heat until onion is tender. blend in flour. cook over low heat stirring constantly until mixture is smooth and bubbly. remove from heat. stir in milk. heat to boiling stirring constantly. boil and stir one minute remove from heat. stir in cheese until melted.

place macaroni in ungreased casserole. stir cheese sauce into macaroni. cook uncovered in 375°F oven 30 minutes.