Preheat oven to 375° F. Spray a baking dish with nonstick cooking spray or rub olive oil with a paper towl. HEAT oil in large, nonstick skillet over medium-high heat. Add onions; cook, stirring occasionally, for 5 to 6 minutes or until soft. Add spinach and 1/4 teaspoon salt; stir until spinach is wilted. Add in the garlic and cook for another 1-2 minutes. Remove from heat.
Combine pumpkin, heavy cream, sage, pepper, remaining 1/4 teaspoon salt and nutmeg in medium bowl.
In another bowl, combine the ricotta, egg, spinach mixture, remaining salt, pepper, and Italian seasoning.
Spread pumpkin sauce onto bottom of dish. Top with noodles, overlapping slightly. Spread spinach and ricotta mixture on top. Repeat layers. Top with remaining 2 noodles and pumpkin sauce. Sprinkle remaining cheese on top and cover with foil or lid.
Bake uncovered for an additional 5 to 10 minutes or until cheese is melted and light golden brown. Let stand for 10 minutes before serving.
