Bring a large pot of lightly salted water to a boil. Add lasagna and cook for 8 to 10 minutes or until al dente; drain.
In large skillet over medium heat, saute onion in the olive oil until tender. Add spinach and stir. Remove from heat and stir in the pesto. In a large bowl mix ricotta cheese, egg, salt, pepper and nutmeg.
In a 3 quart greased baking dish, layer the noodles then the spinach mixture, followed by the ricotta mixture. Sprinkle with mozzarella. Repeat the layers ending with noodles on top. Spread the Alfredo sauce over the top and sprinkle with parmesan.
Cover with foil and bake in a preheated oven for 45 to 55 minutes.