Preheat your oven to 425°F (220°C). A hot oven is crucial for achieving that perfect rise in your biscuits.
In a large mixing bowl, whisk together the cornstarch, gluten-free oat flour, white rice flour, baking powder, salt, xanthan gum, and garlic powder.
Stir in the grated cheddar cheese until it is evenly distributed throughout the flour mixture.
Add the cold butter cubes to the flour mixture. Using a pastry cutter or fork, cut the butter into the flour until the mixture resembles coarse crumbs.
Pour in the cold buttermilk and gently stir until just combined. Be careful not to overmix; some lumps are okay!
Turn the dough out onto a lightly floured surface (using gluten-free flour). Pat it into a rectangle about 1 inch thick. Use a biscuit cutter or a glass to cut out biscuits.
Place the biscuits on a baking sheet lined with parchment paper, spacing them about 1 inch apart. Bake in the preheated oven for 12-15 minutes or until the tops are golden brown.
Remove the biscuits from the oven and let them cool on a wire rack for a few minutes. Serve warm with butter, or enjoy them as they are!
