Preheat oven to 350 degrees F
Butter a 9 x 9 inch baking pan, spread a layer of 1/2 of the sliced squash across the bottom of the pan and sprinkle lightly with garlic salt. Top with 1/2 of the chopped onion, and 1/2 of the sliced tomatoes. Add salt and pepper to taste, then sprinkle 1/2 of the bacon on top. Finally cover it with 1 cup of the shredded cheese.
Repeat this process again for the final layer. Topping with the remaining cheese and a layer of bread crumbs and add half of the shredded cheese. Repeat with another layer of squash, a light sprinkle of garlic salt, onion, tomatoes, salt and pepper, bacon, and all of the remaining cheese.
Bake uncovered, at 350 degrees F for about 1 hour, or until tender. Sprinkle top with basil if desired, and use a slotted spoon to serve.