Adjust oven rack to middle position and heat oven to 450degrees. With a fork, mix flour, baking powder, baking soda, sugar and salt in a medium bowl. Using the large holes on a box grater, coarsely grate butter into the dry ingredients, mix quickly with fingertips to blend evenly. Stir in buttermilk with fork and mix until dough just comes together. If necessary, add extra droplets of buttermilk over any dry patches.