Preheat oven to 450°F (232°C). Line a baking sheet with parchment paper.
In a large bowl, whisk together the gluten-free flour, baking powder, and salt.
Cut in the cold butter using a pastry blender or your fingers until the mixture resembles coarse crumbs. Alternatively, pulse in a food processor until the mixture resembles coarse crumbs.
Add the milk and stir (or pulse in the food processor) until just combined. Do not overmix.
Turn the dough out onto a lightly floured surface and gently pat it into a 3/4-inch thick rectangle.
Use a biscuit cutter or a sharp knife to cut out biscuits. Place the biscuits on the prepared baking sheet.
Brush the tops of the biscuits with melted butter (optional).