Heat olive oil in a large skillet over medium heat. Sauté the onion until transparent and slightly golden, about 5-7 minutes.

Add minced garlic and fresh sage to the skillet, stirring for about 1 minute until fragrant.

Stir in canned pumpkin puree, cooking for 2-3 minutes to meld flavors.

Pour in heavy cream and grated parmesan cheese, stirring until smooth and fully combined.

Season sauce with salt, pepper, and red pepper flakes, letting it simmer for 10-15 minutes.

In a pot, cook pasta in salted water until al dente, about 8-10 minutes. Reserve ½ cup pasta water before draining.

Combine drained pasta with the creamy pumpkin sauce, tossing gently to coat.

Fold in half of crumbled feta cheese and drizzle melted butter on top.

Garnish with remaining feta and toasted pumpkin seeds, then serve hot.