In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add the chopped onion and cook for about 5 minutes until it becomes soft and translucent.

Add 2 minced garlic cloves and 1 tablespoon of chopped fresh sage into the skillet and sauté for an additional 1-2 minutes until fragrant.

Stir in 1 cup of pumpkin puree, cooking for 2-3 minutes until warmed through and bubbling gently.

Pour in 1 cup of heavy cream and add 1/2 cup of grated Parmesan cheese, stirring continuously until smooth.

Season with salt, pepper, and optional red pepper flakes. Simmer on low for 10-15 minutes, stirring occasionally.

Cook 8 ounces of pasta in salted water according to package instructions; reserve 1 cup of pasta water.

Add the drained pasta to the sauce in the skillet, tossing gently and adding reserved pasta water for desired consistency.

Fold in half of the crumbled feta cheese and melt 1 tablespoon of butter if using, stirring until well combined.

Serve hot, garnished with remaining feta and optional pumpkin seeds.