Prepare the Butternut Squash:
Preheat your oven to 400°F (200°C).
Peel and cube the butternut squash, then toss it with olive oil, salt, and pepper. Spread it evenly on a baking sheet.
Roast for 25-30 minutes, or until tender and slightly caramelized.
Cook the Pasta:
While the squash is roasting, bring a large pot of salted water to a boil.
Cook the pasta according to package instructions until al dente. Reserve 1/2 cup of pasta water before draining.
Make the Sauce:
In a skillet, melt the butter over medium heat.
Sauté the onion and garlic until softened and fragrant, about 3-4 minutes.
Add the roasted butternut squash and broth, stirring to combine.
Transfer the mixture to a blender or food processor and blend until smooth. Add the cream and blend again.
Combine Pasta and Sauce:
Return the sauce to the skillet over low heat. Stir in the Parmesan cheese and nutmeg.
Add the cooked pasta to the skillet, tossing to coat. Use the reserved pasta water to thin the sauce to your desired consistency.