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.
*Since there's so much baking powder used in this recipe only use aluminum free baking powder so biscuits don't end up with a slightly metallic-y flavor.
**Don't have a biscuit cutter? Just cut into dough into squares instead.
***Cut biscuits very closely together and just within the outside edge. And don't turn and twist cutter just press firmly and lift or it will seal edges and they won't rise as high.
****Some ovens brown the tops better than others they may only be lightly golden brown, just be careful not to over-bake them so they don't start to dry.