Meat sauce. Heat the oven to 375 degrees F. Brown the beef, sausage, and onion in a large skillet over medium heat 8 to 10 minutes until the meat reaches 160 degrees F, then drain. Add the garlic for 1 minute.
Simmer. Stir in the marinara, diced tomatoes, Italian seasoning, salt, and pepper and simmer 10 to 15 minutes until thick.
Cheese mix. Beat the ricotta, cream cheese, sour cream, egg, Parmesan, 1 cup of the mozzarella, garlic powder, and onion powder until smooth. Do not taste the raw mixture.
Layer. Spread a thin layer of meat sauce in a greased 9 by 13 dish. Add noodles, half of the cheese mix, and meat sauce, repeat once, and finish with noodles and meat sauce.
Bake. Top with the remaining mozzarella, cover with foil, and bake 25 minutes. Uncover and bake 20 minutes more until bubbling and golden.
Rest. Let the lasagna rest 15 minutes before slicing so the layers set.