Cook the pasta according to the package directions for al dente.
Meanwhile, combine the potato, onion and squash in a medium saucepan and cover with water by 1 inch. Bring to a boil and cook until the potato and squash are tender and cooked through, about 8 minutes.
Add the cashews, coconut milk, nutritional yeast, garlic powder, paprika, cayenne, lemon juice and 1 teaspoon salt to a blender along with the cooked vegetables and 1/2 cup of the cooking liquid. Blend until the sauce has the consistency of thick pancake batter; you may need add up to 1/4 cup more of the cooking liquid if your sauce is too thick.
Toss the sauce with the pasta in a large bowl while still hot.
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