Bring a large pot of salted water to a boil. Add the gluten-free elbow macaroni and cook until al dente, about 8-10 minutes. Drain and set aside.

In a medium saucepan, melt the unsalted butter over medium heat, about 2 minutes.

Whisk in the gluten-free all-purpose flour and cook for 1-2 minutes to form a roux.

Gradually whisk in the milk, stirring constantly to prevent lumps, and cook until the sauce thickens, about 3-5 minutes.

Stir in the garlic powder, salt, and pepper, adjusting to taste.

Remove the saucepan from heat and stir in the shredded cheddar and mozzarella cheeses until fully melted and smooth.

Combine the cooked pasta with the cheese sauce, ensuring every noodle is coated.

If desired, preheat the oven to 350°F. Transfer the mac and cheese to a baking dish, sprinkle with gluten-free breadcrumbs, and bake for 15 minutes or until the top is golden brown.

Let the dish rest for 5 minutes before serving.