Preheat oven to 375°F (190°C) and lightly grease a 9×13-inch baking dish.
2. Make the Meat Sauce:
In a skillet over medium heat, cook ground beef with chopped onion until fully browned. Add garlic and cook for 1 more minute. Drain excess grease.
Stir in marinara sauce and Italian seasoning, season with salt and pepper, and simmer for 5 minutes. Remove from heat.
3. Prepare the Cheese Mixture:
In a medium bowl, mix ricotta cheese and sour cream until smooth.
4. Layer the Casserole:
Place half of the frozen ravioli in the prepared baking dish.
Spread half of the ricotta mixture over the ravioli.
Pour half of the meat sauce on top.
Sprinkle with ¾ cup of shredded mozzarella cheese.
Repeat the layering with the remaining ravioli, ricotta mixture, meat sauce, and mozzarella. Finish with grated Parmesan on top.
5. Bake:
Cover the dish with aluminum foil and bake for 25–30 minutes. Remove foil and bake an additional 10–15 minutes, until cheese is melted and bubbly.
6. Serve:
