Impossible Tuna Melt Pie

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

Grease square baking dish, 8 x 8 x 2 inches. Cook onions and butter in 10 inch skillet over low heat, stirring occasionally, until onions are light brown. Sprinkle tuna, 1 cup of the cheese and the onions in dish. Beat baking mix, milk, pepper and eggs with wire whisk or hand beater until almost smooth, about 1 inch. Pour into dish. Bake until knife inserted in center comes out clean, 25 to 30 minutes. Top with tomato slices and remaining cheese. Bake until cheese is melted, 3 to 5 minutes. Cool 5 minutes.
Makes 6 to 8 servings.

http://www.nancyskitchen.com