Preheat your oven to 350°F (175°C).

In a skillet, cook the ground beef with the chopped onion until the beef is browned.

Stir in the marinara sauce and let it simmer for about 5 minutes.

Boil salted water and cook the spaghetti until it's al dente, about 8-10 minutes. Drain and set aside.

Mix the drained spaghetti with softened cream cheese in a large bowl until well coated.

Combine the cottage cheese, ½ cup of Parmesan cheese, and the egg in a separate bowl until smooth.

In a 9×13 casserole dish, layer ½ cup of meat sauce, half of the spaghetti, then cheese mixture, and top with remaining spaghetti.

Spoon the rest of the meat sauce on top and sprinkle with mozzarella cheese.

Cover tightly with foil and bake for 20 minutes.

Remove foil, sprinkle remaining Parmesan cheese, and bake for another 15 minutes until cheese is bubbly and golden.

Let cool for 10 minutes before slicing.