Preheat oven to 350°F (175°C).

In a large frying pan, brown ground beef with chopped onion and minced garlic.

Drain off any excess fat from the pan.

Add spaghetti sauce and tomato sauce to the beef mixture; cover and simmer for 15 minutes.

In a medium bowl, combine thawed spinach, cottage cheese, mozzarella cheese, Parmesan cheese, parsley flakes, and black pepper.

Layer the beef mixture, cheese mixture, and lasagna noodles (if using) in a baking dish.

Repeat layers until all ingredients are used, finishing with a layer of mozzarella cheese on top.

Cover the baking dish with foil and bake for 30 minutes.

Remove the foil and bake for an additional 20 minutes, or until the cheese is melted and bubbly and the lasagna is heated through.

Let stand for 10 minutes before serving.