Fry bacon and onion together. Slice zucchini 1/4-inch thick. Cook in a small amount of water for 2 minutes. Drain. In 1 1/2 quart baking dish layer in the following order, zucchini, bacon, onion, and cheese. Top with tomato sauce. Bake at 350 degrees for 30-40 minutes. Makes 6-8 servings.