1 (7 oz.) pkg. elbow macaroni
1 tbsp. butter
1/4 c. chopped onion
1 can cream of mushroom soup
1/2 c. milk
2 c. shredded sharp cheese
1 (16 oz.) can tomatoes, cut up

Cook macaroni and drain. In medium saucepan, melt butter, add onion, cook until tender. Add soup and milk. Add cheese and tomatoes. Cook, stirring constantly until cheese melts. Combine macaroni with mixture. Pour into 1 1/2 quart casserole. Bake at 350 degrees for 30 minutes. Serves 4.