The combination of sweet tomatoes and zucchini with melted cheese in this zucchini-tomato casserole tastes like a summer-fresh pizza. It's the perfect easy side dish for any summer meal.
Place oven rack in middle position; preheat to 375°F. Coat a 13-by-9-inch (3-quart) broiler-safe baking dish with cooking spray. Combine fontina, basil, sun-dried tomatoes, 2 tablespoons Parmesan, crushed red pepper and salt in a medium bowl. Stir panko, oregano, garlic powder and the remaining 2 tablespoons Parmesan together in a small bowl.
Sprinkle 1/4 cup of the panko mixture over the bottom of the prepared baking dish. Arrange half of the zucchini slices in an even layer, slightly overlapping, on the panko mixture. Arrange half of the tomato slices on top of the zucchini and sprinkle with half of the cheese mixture. Repeat the layers of zucchini, tomato and cheese. Sprinkle the remaining panko mixture over the cheese.
Cover tightly with foil and bake for 15 minutes. Remove the foil and continue to bake until the vegetables are tender and the cheese is melted, about 20 minutes more.
Set oven to broil. (Do not remove casserole from oven.) Broil until the topping is golden brown in spots, 2 to 3 minutes. Let stand for 5 minutes before serving.