Preheat your oven to 350°F while preparing your ingredients.

Cook the spaghetti in a large pot of salted boiling water until al dente, then drain and return to pot with 24 oz of marinara sauce.

In a skillet, cook the Italian sausage, chopped onion, and minced garlic over medium heat until no pink remains. Drain excess fat and add remaining marinara and Italian seasoning.

In a mixing bowl, whip together the cottage cheese, cream cheese, sour cream, and 1 cup of mozzarella until smooth.

Grease a 9x13-inch baking dish. Layer half of the spaghetti, then the cheese mixture, remaining spaghetti, and finally the meat sauce.

Bake uncovered for 35-45 minutes, adding remaining mozzarella 20 minutes before it's done.

Let the casserole rest for 15 minutes before serving.