Preheat oven to 475 degrees.
Combine breadcrumbs, Parmesan, and one Tbsp oil. Set aside.
In a large cast-iron skillet, brown ground beef over medium high heat.
Add pasta sauce and water. Bring to a simmer.
Stir in the rice.
Top with onion, the carefully arrange zucchini in a single, slightly overlapping layer.
Season with salt and pepper, drizzle with remaining Tbsp of oil, and top with breadcrumb mixture.
Cover with foil and bake in oven for 10 minutes.
Remove foil and bake until rice is cooked through and breadcrumbs are golden, about 5-10 more minutes. (Add more water before baking if needed to prevent crunchy rice.)
Let cool for 5 minutes before serving!