Preheat oven to 400°F. Grease a deep 9 x 13-inch baking dish; set aside.
Squeeze all of the liquid out of the spinach. I like to use a dish towel for this, and just keep squeezing until you wring out as much water as possible. Place spinach in a large bowl. Add ricotta, 1 cup of the mozzarella, ¼ cup of the Parmesan, egg, basil, oregano, salt, garlic powder, and nutmeg to the bowl with the spinach. Stir really well with a fork to combine.
Spread about ½ cup of the marinara sauce in the bottom of the prepared baking dish. Top with 3 no-boil lasagna noodles (or as many as you need to cover a single layer in the dish), ½ of the ricotta mixture, and ¾ cup of marinara sauce.
Add 3 more noodles to the dish, the remaining ½ of the ricotta mixture, and ¾ cup of marinara sauce. Finally, add another layer of 3 noodles, spread remaining ¾ cup of marinara sauce on top, and sprinkle with the remaining 1 cup of mozzarella cheese and the remaining ¼ cup of Parmesan cheese. Cover the dish with aluminum foil.
Bake for 35 minutes. Remove foil, and bake for another 5-10 minutes (or until heated through and cheese on top is browned). Let stand for at least 15 minutes before slicing and serving.