Preheat oven to 425 degrees and line a baking sheet with a silicone baking mat or parchment paper.
Add the gluten-free flour, xanthan gum, salt, baking powder, baking soda, black pepper, and parmesan cheese to a large bowl and whisk together to combine.

Add the cubed butter and cut in with a pastry cutter or two forks until it resembles coarse crumbs.

Stir in ¾ cup buttermilk and mix until just combined.

Turn the dough out onto a floured surface and pat into a rectangle. Fold the rectangle into 3rds and turn the dough a half turn. Then flatten into a rectangle until the dough is about a ½-¾ inch thick.

Cut the dough with a 2 ½ inch biscuit cutter and place the biscuits on the prepared baking sheet.

Re-roll the dough as needed, there should be about 12 biscuits.
Refrigerate the biscuits at least 30 minutes to ensure that the butter stays nice and cold. This is especially important if your house/kitchen is warm and humid.

Brush the tops of the biscuits with the remaining buttermilk. Sprinkle the tops of the biscuits with additional parmesan cheese and cracked black pepper if desired.

Bake for 12-15 minutes or until the biscuits are browned and baked through.