Preheat the oven to 350°F. Spray an 8x8-inch bakng dish with non-stick cooking spray.
In a large skillet over medium heat, melt the butter. Add the onion and cook, stirring frequently, for 2 minutes. Add garlic and continue cooking for 30 seconds. Add the zucchini and Italian seasoning, stirring to coat with butter, and cook for an additional 2 minutes until golden.
In the prepared baking dish, layer 2 tablespoons seasoned bread crumbs, onion and zucchini mixture, remaining 2 tablespoons bread crumbs, tomatoes, and cheese.
Bake for 20 minutes, until cheese is melted, and serve hot.