Heat a small saucepan to medium heat. Add butter.

Once butter is completely melted, add flour and whisk to combine. Let cook for 30 seconds. Add sriracha and whisk again. Add milk and whisk well. 

Let cook for 4-5 minutes, over medium heat, until mixture starts to simmer and thicken. Stir every minute or so to prevent sticking. Once thick enough to coat the back of a wooden spoon, turn off heat.

Off the heat, add the cheddar cheese. Whisk until melted. Add the salt and garlic powder and more sriracha if desired. 

Serve immediately.