Preheat the oven to 450°F (232°C).
In a large bowl add the gluten-free flour, baking powder, salt, sugar, and give it a quick whisk or stir to combine the ingredients.
Cut the butter into small pieces and put in the freezer for 10 minutes. Keep the buttermilk cold.
Cut in butter (or shortening for dairy-free) into the flour with a pastry cutter or fork until it looks like the size of small peas.
Add in the buttermilk and the whisked egg (or egg replacer) and stir until a soft dough forms. The dough will be sticky.
Add one tablespoon of flour to a large piece of parchment paper.
Place the dough on top of the floured parchment paper. Dust the top of the dough with 1 tablespoon of flour and gently fold dough over on itself 2 times.
With your hands form a dough round that is about 7 inches in diameter and 1 inch thick.
Cut out 2-inch biscuits using a biscuit cutter. Do not twist cutter when cutting. Put the biscuits on a greased large cast iron pan or baking sheet.
Bake the biscuits for 15-20 minutes at 450°F (232°C). At the 15-minute point check your biscuits to see if they are golden brown.
Brush melted butter on top of the warm biscuits. Serve warm and enjoy!