Preheat oven to 425 degrees. Spray 4-quart baking dish with nonstick cooking spray
Prepare pasta according to package directions. Reserve 1/2 cup pasta cooking water and set aside for later use. Drain pasta; return to cooking pot
Combine pumpkin, flour, garlic powder, salt, nutmeg and cayenne pepper in medium skillet over medium heat. Slowly add evaporated milk, stirring until smooth. Cook, stirring occasionally for 2 to 3 minutes or until mixture begins to thicken slightly. Pour pasta in pot. Add sausage and reserved pasta cooking water; stir well
Spread half of pasta mixture into prepared baking dish. Top with spinach. Cover with remaining pasta mixture. Lightly spray a piece of foil with nonstick cooking spray. Cover ziti with foil, greased side down
Bake 20 minutes or until heated through. Combine mozzarella and Parmesan cheeses in small bowl. Remove foil; sprinkle with cheese mixture. Bake, uncovered for an additional 5 minutes or until cheese is melted.
