Cook the pasta in salted water according to package directions until al dente. Drain well and set aside.
Melt the butter over medium heat in a medium pot. When the butter is melted, whisk in the flour, salt, pepper, onion powder, and mustard powder and cook for 1-2 minutes.
Slowly whisk in the milk until smooth. Cook over medium heat, stirring constantly, for about 3 minutes until the sauce is thickened. Turn off the heat and stir in the cheese until melted.
Add the cooked pasta to the cheese sauce and stir well to combine. Serve hot.
Notes
Notes: Using room temperature milk will speed up the thickening process when making the sauce. If the sauce is too thick for your liking, you can thin it out with more milk.