Cook the pasta according to the directions on the packet until al dente.
Cook the veggies: Add the potatoes, carrots, onion, and a dash of salt to a medium saucepan with enough water to cover by about 2 inches high. Bring the water to a simmer and cook covered for about 12 minutes, or until tender. Drain, reserving 2 cups of the cooking water (vegetable broth).
Blend the sauce: Transfer the potatoes, carrots, onion, cashews or white beans, nutritional yeast, lemon juice, mustard, garlic powder, smoked paprika, cayenne, and 1 cup of the vegetable broth to a blender. Blend on high until smooth.
Heat the sauce and pasta: Pour the sauce into a small nonstick skillet. Add the desired amount of cooked pasta and cook over medium-low heat until warmed through, adding more vegetable broth until the desired consistency.
Season with lemon zest, salt and pepper. Serve immediately.