Virtual Sefer Baked Zucchini Gratin

1 onion. sliced
2 lbs zucchini sliced
1 stick butter melted and divided
2 cups shredded mozzarella cheese
1/2 cup bread crumbs
1/4 grated parmesan cheese
in a lightly greased 2 qt baking dish, layer onion and zucchini. Drizzle with 1/4 cup butter, sprinkle with mozzarella cheese. In a seperate bowl, combine remaining butter, bread crumbs and parmesan cheese. Sprinkle crumb mixture evenly over top. Bake uncovered, at 350 for 35-40 minutes or until zucchini is tender. Serves 8