$5,000 Casserole

This is a really old recipe that my sister gave to me many years ago. I haven't made it in a long time but we used to really love it.

1 lb. ground beef
1 cup chopped onion
Brown in skillet and drain fat.
add:
1 can Cream of Mushroom soup
1/4 tsp. pepper
1 tsp. salt
1 8 oz. carton sour cream
1 15 oz. can peas(drained)
1 7 oz. pkg. macaroni (cooked according to pkg. directions, and drained)
Put all in greased casserole dish and bake 35 min. in 350 degree oven.