1. Preheat oven to 375°F.
2. In small skillet heat oil, add onion and sauté until tender, add mushrooms and 1/4 tsp. salt. Heat about 2 minutes until mushrooms are heated through. Set aside.
3. In a small bowl, combine pumpkin, half and half, sage, pepper, and remaining 1/4 tsp. salt.
4. Spread 1/2 c. pumpkin sauce in an 11 X 7-in. baking dish lightly coated with cooking spray.
5. Top with 3 noodles (noodles will overlap slightly). Spread 1/2 c. pumpkin sauce to edges of noodles. Top with half of mushroom mixture, 1/2 c. ricotta cheese, 1/2 c. mozzarella and 1/4 c. Parmesan cheese. Repeat layers. Top with remaining noodles and pumpkin sauce.
6. Cover and bake in preheated oven for 45 minutes. Uncover; sprinkle with remaining Parmesan cheese. Bake 10-15 minutes longer or until cheese is melted. Let stand for 10 minutes before cutting.