Boil your macaroni, or preferred pasta noodle, in a large pot of salted water. Cook until al dente. Drain and set aside.
Heat the milk in a saucepan or in the microwave until very hot, but not quite boiling.
Melt the butter over medium heat in a large pot or saucepan. Add the flour and whisk continuously for 3-4 minutes. The mixture should start to turn a light brown color.
Continue to whisk the mixture while slowly add the hot milk. Keep whisking, and cook for another 3-5 minutes. The sauce should start to thicken up.
Add the ground salt, mustard powder, garlic powder and cayenne pepper. Stir to combine.
Reduce heat to low and add the grated cheeses. Stir until the cheese until completely melted and the sauce is smooth and creamy. Season with additional salt/pepper to taste.
Pour sauce over your prepared pasta. Mix well to coat the pasta. Serve hot.