Bring 3 cups of water to a boil in a medium sauce pan.
Add potatoes, carrots and onions.
Bring back to a boil and reduce heat to low until vegetables are tender.
Drain water, reserving liquid, and add vegetables to Vitamix.
Add 1 1/2 cup of reserved water, cashews, coconut milk, nutritional yeast, lemon juice, garlic powder, salt and cayenne pepper to Vitamix.
Blend on high until ingredients are nice and creamy, less than a minute.
Add pasta to a serving dish, or back into the large pot, and pour the "cheese" sauce over the pasta.
Mix well and serve.