1 sm. onion, chopped
1/2 c. butter
2 (6 1/2 oz.) cans tuna, drained
2 c. cheddar cheese, shredded
1/4 tsp. salt
3 eggs
1 c. Bisquick
1 1/4 c. milk
1/8 tsp. pepper
2 tomatoes, thinly sliced

Grease an 8 x 8 x 2 inch baking dish. Cook onions and butter in skillet until onions are soft. Sprinkle tuna, 1 cup cheese and onions in dish. Beat Bisquick, milk, salt, pepper and eggs until almost smooth. Pour in baking dish. Bake at 400 degrees for 25 to 30 minutes. Top with tomato slices and cheese. Bake just until cheese is melted.