Preheat your oven to 375°F (190°C) and position an oven rack in the top third.

In a mixing bowl, combine the cream cheese, ricotta, and parmesan, along with garlic powder and dried oregano; beat until smooth.

Boil salted water in a large pot, add the uncooked spaghetti, and cook for 2 minutes less than the package directions; drain excess water.

Heat a large skillet, add Italian sausage and chopped onion, and sauté until browned (5-7 minutes). Then, add minced garlic and red pepper flakes.

In a large mixing bowl, combine the drained spaghetti with the sausage mixture and marinara sauce, mixing gently until well-coated.

Spread half of the pasta mixture in a 9x13-inch baking dish, dollop with the creamy cheese layer, then top with remaining pasta and mozzarella cheese.

Cover with foil and bake for 30 minutes, then broil for 2-4 minutes until the cheese is golden.

Let the dish sit for 5-10 minutes before serving. Adjust seasoning with salt and pepper as needed.