Preheat the oven to 375°F (190°C).

In a large bowl, combine the pumpkin puree, ricotta cheese, beaten egg, garlic, oregano, basil, salt, pepper, and nutmeg. Mix until well combined.

In a separate bowl, mix 1 cup of the mozzarella cheese with the chopped spinach.

Spread a thin layer of marinara sauce on the bottom of a 9x13 inch baking dish.

Layer 3 lasagna noodles over the sauce, followed by half of the pumpkin mixture, half of the spinach and mozzarella mixture, and a third of the marinara sauce.

Repeat the layering: place 3 more noodles, the remaining pumpkin mixture, the remaining spinach and mozzarella mixture, and another third of the marinara sauce.

Top with the final 3 lasagna noodles, the remaining marinara sauce, and sprinkle the remaining mozzarella and Parmesan cheese on top.

Cover the baking dish with aluminum foil and bake for 25 minutes.

Remove the foil and bake for an additional 15-20 minutes, or until the cheese is bubbly and golden.

Let the lasagna cool for 10 minutes before slicing and serving.