Preheat oven to 425°F.
Cut the butternut squash in half lengthwise, scoop out the seeds, and place them, cut side down on a parchment-lined sheet pan. Cut the onion into 1-inch wedges, drizzle with a little olive oil, and place next to the butternut. Roast until tender, 30-45 minutes, depending on size, tossing the onions halfway through and removing them early, when tender.
Scoop out 2 heaping cups of roasted butternut squash and add it to the blender along with the onions, broth, olive oil, salt, pepper, nutmeg, sage, and miso paste. If you want to add pecorino, blend it as well. Blend until silky smooth.
Place it in a saucepan and heat it up. You will want to drink it like soup, and sometimes I do this too.
Taste and season, adjusting the salt, pepper, and nutmeg as needed. Add a pinch of cayenne if desired.
Toss the warm pasta sauce with your favorite pasta.
