In a medium bowl use a whisk to sift together flour, sugar, baking powder, baking soda and salt.
To the bowl add the buttermilk mixing until the sifted dry ingredients are fully moistened.
Add 7 Tbsp melted butter to a 9x9-inch or 8x8-inch baking dish swirling to coat the bottom and sides.
Dollop the biscuit dough over the butter then use an offset spatula to spread the biscuit dough evenly into the dish. Drizzle the top with the reserved 1 Tbsp melted butter. Use a sharp knife to score the dough into 9 equal squares.
Bake for 22-25 minutes or until puffed and the top is golden.
Let stand 5 minutes or until the butter is absorbed, then cut along the scored lines into squares and serve.