Bring a large pot of lightly salted water to a boil. Add lasagne and cook for 8 to 10 minutes or until al dente; drain.
In large frypan 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 litre greased baking dish, layer the pasta then the spinach mixture, followed by the ricotta mixture. Sprinkle with mozzarella. Repeat the layers ending with pasta 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.