In a large pot, bring salted water to a boil. Add the fettuccine and cook according to package instructions until al dente. Reserve 1 cup of pasta water, then drain the pasta and set aside.
In a large skillet, heat olive oil over medium heat. Add the chopped onion and sauté for about 3-4 minutes until translucent. Add the minced garlic and sage, cooking for an additional 1-2 minutes until fragrant.
To the skillet, add pumpkin puree, heavy cream, and vegetable broth. Stir well to combine. Bring the mixture to a gentle simmer, allowing it to thicken slightly (about 5 minutes).
Stir in the grated Parmesan cheese, mixing until melted and smooth. Season with salt, pepper, and a pinch of nutmeg if desired.
Add the cooked fettuccine directly into the sauce, tossing gently to coat. If the sauce is too thick, gradually add some reserved pasta water until the desired creaminess is achieved.
Plate the creamy pumpkin sage pasta into bowls or on plates, garnish with toasted pumpkin seeds and extra Parmesan if desired.
Notes
Garnish with toasted pumpkin seeds for added texture.