In a medium saucepan over medium heat, melt the 2 tablespoons of unsalted butter. Allow it to bubble slightly but be careful not to let it brown.
Add the 2 tablespoons of all-purpose flour to the melted butter. Whisk continuously for about 1-2 minutes until the mixture forms a paste (this is called a roux). It should be bubbly and slightly golden.
Slowly pour in the 1 cup of whole milk while whisking vigorously. This ensures that the flour mixture integrates smoothly into the milk, preventing lumps. Continue to whisk until the mixture thickens, about 3-5 minutes.
Once the sauce has thickened, reduce the heat to low and gradually add the 1 ½ cups of grated cheese. Stir until the cheese is completely melted and the sauce is smooth.
Mix in the ¼ teaspoon of onion powder, ⅛ teaspoon of garlic powder, ¼ teaspoon of kosher salt, and ¼ teaspoon of black or white pepper. Taste and adjust the seasoning if necessary. If you like a bit of heat, sprinkle in some cayenne pepper at this stage.
Your Cheddar Cheese Sauce is ready to be served! Pour it over your favorite dishes or use it as a dip. Enjoy the creamy goodness!