Combine squash and 1 tablespoon oil on a baking sheet; toss until coated.
Roast in the preheated oven until tender and lightly browned, about 25 minutes.
Bring a small pot of water to a boil. Add cashews; simmer until softened, about 20 minutes. Drain.
Combine cashews and 1 1/2 cup broth in a blender; blend until very smooth. Add roasted squash, remaining 1/2 cup broth, miso, nutritional yeast, and lemon juice; blend until sauce is combined.
Bring a large pot of lightly salted water to a boil. Cook bow-tie pasta, stirring occasionally, until tender yet firm to the bite, about 11 minutes. Drain, reserving 1 cup pasta water. Transfer pasta to a serving bowl.
Heat remaining 2 tablespoons oil in a skillet over medium-high heat. Add onion and salt; cook and stir until golden brown, about 9 minutes. Add sage and stir until fragrant, about 1 minute. Pour in cider; cook, stirring up browned bits from the bottom of the skillet, 1 to 2 minutes.
Stir half of the cashew sauce into the pasta. Add onion mixture. Stir in enough reserved pasta water to thin and warm sauce. Season with pepper. Garnish with parsley.
Instead of boiling, cashews can be soaked in cold water for 2 to 12 hours. Or, if you have a high-powered blender, you can get away with not soaking them at all; just be sure to blend them until smooth.
A 15-ounce can of pumpkin or squash puree can be substituted for the roasted butternut squash.
Substitute 1/4 teaspoon dried ground sage for the fresh if desired.
This recipe makes 2 1/2 cups extra sauce, which you can freeze in an airtight container for another day.
Per Serving: 626 calories;24.6 g fat;
86.2 g carbohydrates;
21.9 g protein;
0 mg cholesterol;
624 mg sodium.