In a large skillet, cook the ground beef over medium heat until browned. Add the onion and garlic and cook until the onion is softened.
Stir in the pumpkin puree, ricotta cheese, mozzarella cheese, Parmesan cheese, parsley, basil, oregano, nutmeg, salt, and pepper. Cook until heated through.
Preheat the oven to 375°F (190°C).
Spread a thin layer of marinara sauce in the bottom of a 9x13 inch baking dish. Layer with lasagna noodles, followed by a layer of the pumpkin mixture. Repeat the layers until all ingredients are used, ending with a layer of the pumpkin mixture.
Cover the dish with foil and bake for 45 minutes. Remove the foil and bake for an additional 15 minutes, or until the lasagna is bubbling and the top is golden brown.
Let the lasagna cool for a few minutes before serving. Enjoy!