Preheat oven to 450 degrees. Mix all the dry ingredients together in a large bowl, make a well in the center and pour all of the buttermilk in at once. Using 1 hand, stir in a full circle starting in the center of the bowl working towards the outside of the bowl until all the flour is incorporated. The dough should be soft but not too wet and sticky. When it all comes together, a matter of seconds, turn it out onto a well-floured board. WASH AND DRY YOUR HANDS. Roll dough around gently with floured hands for a second, just enough to tidy it up, flip the dough over. Pat the dough into a round about 1 1/2-inches deep. Sprinkle a little flour onto the center of a baking sheet and place the loaf on top of the flour. Cut a deep cross on it with a sharp knife, prick the four sections to let the fairies out. Let the cuts go over the sides of the bread to make sure of this.
Bake in preheated oven for 20 minutes, then reduce the heat to 400 degrees for 20 minutes, or until just cooked. If you are in doubt, tap the bottom of the bread: if it is cooked it will sound hollow. Cool on a wire rack.