Preheat oven to 350F. In a nonstick skillet, heat 1 tablespoon olive oil over medium high heat until hot but not smoking. Add onions; stir to coat evenly with oil. Add water to pan and cover. Cook, stirring frequently, until onions are softened, 15 to 18 minutes. While onions are cooking, season the bread crumbs with salt and pepper. Set aside. Break corn cobs in half, then slice off kernels.
When onions are thoroughly cooked, turn off heat. Add corn to onions; stir until corn and onions are evenly distributed. Season with salt, pepper and parsley.
Lightly spray a 9-inch square baking dish with olive oil or cooking spray. Spread one-third of the bread crumbs in the baking dish. Top with a layer of tomatoes, then half of the onion and corn mixture. Repeat layers, finishing with tomato slices. Spray (or drizzle 1 teaspoon) olive oil over the tomatoes. Bake for 35 to 40 minutes, or until heated through. Serve immediately.
* Note: You can use frozen corn, but buy the best you can get.
Serves 4 as an entree, 8 as a side dish