Add the pumpkin puree, almond milk, nutritional yeast, cashews, garlic, salt, and onion powder to a blender and blend until smooth and creamy.
Bring a large pot of salted water to a boil and cook the macaroni until al dente, about 7 minutes. Strain and add the macaroni back to the pot. Pour in as much pumpkin “cheese” sauce as desired and stir to combine. (You might like to use all of the sauce or you may prefer less, depending on how saucy you like it.) Scoop into bowls, sprinkle with pepper, and serve.