01 -
Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish and set aside.
02 -
In a large skillet over medium heat, cook the ground beef with diced onion until the meat is browned and the onion is soft. Drain any excess grease, then season with garlic powder, salt, and pepper.
03 -
Add the tomato sauce, cream of mushroom soup, and sour cream to the skillet with the beef mixture. Stir until well combined and heated through.
04 -
Spread half of the cooked pasta in the bottom of the greased baking dish. Layer half of the beef mixture over the pasta, then sprinkle with half of the shredded cheddar cheese. Repeat the layers with the remaining pasta, beef mixture, and cheddar cheese.
05 -
Sprinkle the mozzarella cheese evenly over the top layer.
06 -
Cover the casserole with foil and bake for 20 minutes. Remove the foil and bake for an additional 10 minutes, or until the cheese is melted and bubbly.
07 -
Remove from the oven, garnish with chopped parsley if desired, and serve warm.