1. Preheat oven to 400 degrees. Combine squash puree, 1 teaspoon salt, sage, and 1/4 teaspoon pepper in medium bowl; mix well. Combine ricotta, 1/4 cup Parmesan, 1/2 teaspoon salt, and 1/4 teaspoon pepper in second bowl, and mix well.
2. Coat 8x8-inch baking dish with cooking spray. Place 2 noodles in bottom of dish, overlapping slightly. Spread half of squash mixture over noodles. Layer 2 more noodles on top, and spread with half of ricotta mixture. Repeat layers-noodles, squash, noodles, ricotta, then sprinkle with remaining 1/4 cup Parmesan.
3. Cover baking dish with foil. Bake 45 minutes, remove foil, and bake 20 to 25 minutes more, or until golden on top. Let stand 5 to 10 minutes before serving.