Bring a large pot of salted water to a boil. Add the gluten free pasta and cook according to package directions, stirring often to prevent sticking, until tender but not mushy.

Drain the cooked pasta well using a colander and set it aside. Avoid rinsing so the sauce clings better when everything is combined later.

Place a medium saucepan over medium heat. Add butter and let it melt slowly, stirring gently, until fully melted but not browned.

Whisk the gluten free flour into the melted butter. Cook for about one minute while whisking constantly to remove any raw flour taste.

Slowly pour in the milk and heavy cream while whisking. Let the mixture simmer for three to four minutes until smooth, slightly thickened, and creamy.

Lower the heat and add shredded cheddar and mozzarella cheese. Stir gently until melted, then season with salt, pepper, garlic powder, and mustard powder.

Add the cooked pasta to the cheese sauce. Stir until every piece is coated and cook together for one to two minutes so flavors fully combine.