Fill a large pot with water and bring to a boil. Add a small handful of salt and pasta and stir. Stir pasta occasionally and cook until al dente, about 6 to 8 minutes. Drain, reserving 1 cup pasta water. Toss pasta with 2 teaspoons of oil and set aside.
Pour oil into a large saucepan and place over medium-high heat. Add squash and onion and sauté for 6 to 7 minutes. Add garlic, sage, season with salt and pepper and continue to sauté for 2 to 3 minutes.
Pour stock into the mixture and lower the heat to medium. Simmer until squash is fork tender, about 7 to 9 minutes.
Pour mixture into a blender and puree until smooth (make sure the center top lid has been removed and covered with a kitchen towel to prevent the hot mixture from exploding). If the mixture is too thick, add the reserved pasta water, as needed, until desired consistency is achieved.
With the motor running, remove the kitchen towel from the opening in the lid and add the cashews and buttery spread. Continue to blend until fully incorporated and the mixture is smooth. Adjust seasonings.
Place pasta into a large mixing bowl and top with sauce. Toss together. Garnish, if using, and serve immediately.
Notes
**Nutritional Information Does Not Include Optional Garnishes**