Preheat the Oven: Begin by setting your oven to preheat at 400 degrees Fahrenheit (204 degrees Celsius). Concurrently, apply a nonstick cooking spray to a 9x13-inch baking dish to prevent sticking.
Prepare the Meat Sauce: In a large skillet over medium heat, cook the ground beef until it is thoroughly browned and no longer pink, ensuring it is crumbled for even cooking. Drain any excess grease and stir in the marinara sauce. Remove from heat and set aside.
Combine the Cheese Mixture: In a substantial mixing bowl, blend the softened cream cheese, sour cream, half of the Parmesan cheese, garlic powder, Italian seasoning, and salt until the mixture achieves a uniform and smooth consistency. Carefully add the frozen ravioli to the bowl, folding gently to coat each piece evenly without breaking.
Assemble the Casserole: Pour the ravioli and cheese mixture into the prepared baking dish, creating an even layer. Proceed to evenly distribute the meat sauce over the ravioli layer. Sprinkle the surface with the remaining Parmesan cheese and one cup of mozzarella cheese.
Bake: Cover the dish tightly with aluminum foil and place in the preheated oven. Bake for 30 minutes. Afterward, remove the foil and continue baking for an additional 15 minutes, or until the cheese is bubly and golden brown.
Cool and Serve: Allow the casserole to rest for 10 minutes after removing it from the oven. This resting period helps the layers set for easier slicing. Serve warm and enjoy the rich, layered flavors of your Million Dollar Ravioli Casserole.