Make the pasta. Bring a large pot of water to a boil. Add the salt followed by the pasta. Cook to al dente according to the instructions on the package.
Make the sauce. Heat the olive oil in a large saucepan over medium-high heat. Add the onions and sauté for 3 minutes or until translucent. Add the ground beef and Italian sausage and season with ground black pepper and garlic powder. Cook the meat, breaking it apart with a wooden spoon until browned. Add the marinara sauce and stir to combine. Reduce the heat to low and simmer for 20 minutes.
Make the cheese mixture. Whisk together the ricotta, sour cream, and cream cheese.
Assemble. Toss together the sauce and the pasta until thoroughly coated in the sauce. Spread half of the pasta mixture in a 9x13-inch baking pan. Spread the cheese mixture evenly over the pasta. Scatter 1 cup of mozzarella cheese over the top. Spread the rest of the pasta over the cheese mixture. Top with the remaining mozzarella and Parmesan.
Bake. Bake uncovered for 40 minutes or until the cheese is bubbly.