Bring a large pot of water to a boil over medium-high heat.
Add the cauliflower and sweet potato and cook for about 10 minutes or until soft when poked with a fork. Use a large slotted spoon to transfer the veggies to a blender, draining off all the liquid.
Add the milk, cheese, butter, salt, and garlic powder, if using, to the blender with the veggies and puree until completely smooth.
Meanwhile, bring the water back to a boil and cook the pasta according to package directions. Drain and return to the pot.
Stir in the cheese sauce, season to taste with additional salt, if needed, and serve warm.
