Found from http://old.post-gazette.com/food/20021003mailbox1.asp and want to try this.

1 tablespoon butter or margarine
2 tablespoons chopped onion
2 tablespoons chopped green pepper
10 3/4-ounce can cream of mushroom soup
3/4 cup milk
1 cup shredded American cheese
1/2 pound spaghetti, cooked and drained
2 (6 1/2-ounce) cans tuna

1 tablespoon butter or margarine 2 tablespoons chopped onion 2 tablespoons chopped green pepper 10 3/4-ounce can cream of mushroom soup 3/4 cup milk 1 cup shredded American cheese 1/2 pound spaghetti, cooked and drained 2 (6 1/2-ounce) cans tuna

Melt butter in saucepan and cook onion and pepper until softened. Stir in soup, milk and cheese. Stir over low heat until cheese melts, then add spaghetti and tuna.

Turn into casserole dish and bake at 350 degrees for 20 to 30 minutes or until top is browned. Serves 4-6.