In a pot of boiling water, cook the macaroni until just near tender, do not over cook, basically under cook it by a minute or so. Drain and rinse under cold water, the cold water will stop the cooking process. Add the pasta to your slow cooker.
Add the onion powder, mustard, soup, sour cream, mayo, and black pepper to the slow cooker.
Give the slow cooker a stir to mix everything together.
Add the cheese and mix that in.
For a Variant, I added to the slow cooker about 500 grams (1 lb) of cheese stuffed smoked sausage that I had sliced.
Mix the sausage in. Cook on Low setting for 3 hours.
Stir once or twice during the cooking but quickly so not all the heat is let out of the cooker.
Serve and enjoy.