Preheat oven to 450 degrees. Line an 18 by 13-inch baking sheet with a silicone baking liner or with a sheet of parchment paper that's oven safe to 450 degrees.
In a large mixing bowl whisk together flour, baking powder, sugar, baking soda and salt for 20 seconds.
Cut 7 Tbsp cold butter into small cubes. Add to flour mixture and cut butter into mixture with a pastry cutter until there are small clumps of butter about the size of peas, make a well in the center of mixture.
Pour buttermilk into well then fold mixture with a rubber spatula until it comes together. Gently turn and press dough to bring together completely, then drop onto a lightly floured surface.
Gently roll dough out to a large rectangle, about 10 by 9. Fold in half then repeat gently rolling and folding process twice more.
Gently roll and shape final rectangle to 9 1/2-inches by 4 3/4-inches (nearly 1-inch high).
Dip a 2 1/4-inch or 2 1/3-inch round biscuit cutter** in flour, cut dough into 8 rounds***.
Transfer to baking sheet spacing apart. Bring remaining dough scrapes together and gently press and form a small rectangle, cut 2 more biscuits, transfer to baking sheet.
Bake in preheated oven 11 - 13 minutes until golden brown and cooked through****. Brush with 1 Tbsp melted butter and serve warm.