Preheat oven to 400°. Sprinkle heavy large baking sheet with 2 tbsp flour. Sift 3 cups flour into bowl of heavy duty mixer fitted with a paddle attachment (or do it by hand). Add 1 tbsp baking powder, 1 tsp salt and mix until combined. Gradually beat in enough buttermilk to form slightly moist dough. Turn out dough onto lightly floured work surface and knead until dough is smooth, about 1 min. (do not overwork or dough will be tough). Form dough into ball and transfer to prepared baking sheet. Flatten dough into 7 inch diameter round. Using a small sharp knife, cut 1/4 inch deep crisscross lines into top of dough round. Bake until bread turns brown and sounds hollow when tapped on bottom, about 40 min. Wrap warm bread in clean kitchen towel and cool completely. Slice bread and serve.