2 c. cooked elbow macaroni
1/3 c. mayonnaise
1/4 c. finely chopped onion
1 (10 1/2 oz.) can cream of mushroom soup
1/2 c. milk
1 c. shredded cheese (Cheddar or American)

Combine macaroni with mayonnaise and onion. Blend together soup, milk and 1/2 cup of cheese. Stir into macaroni; place into 1 1/2 quart casserole. Top with additional 1/2 cup cheese. Bake at 400 degrees for 20-25 minutes.