Melt the butter in a heavy bottomed saucepan over medium heat and whisk in the flour. Continue whisking and cook for 2 minutes.
Slowly add the milk, whisking constantly. Cook until the sauce thickens, about 10 minutes, stirring frequently. Remove from the heat.
Add the cheese, salt, chili powder, and garlic powder. Stir until the cheese is melted and all the ingredients are incorporated, about 3 minutes. Use immediately or refrigerate for up to 3 days.