Preheat the oven to 425°F degrees. Place a large cast iron dutch oven with lid into the oven as it preheats.
In a large bowl sieve and combine all the dry ingredients.
Add the buttermilk to form a sticky dough. Place on floured surface and lightly knead (too much allows the gas to escape).
Shape into a round flat to fit into the dutch oven and cut a cross in the top of the dough. Place dough on a large sheet of parchment paper.
Carefully remove the dutch oven from the preheated oven and remove lid. Gather parchment paper by the edges and lift to place the loaf and parchment together into the dutch oven and cover with the lid.
Bake for 30 minutes. Remove cover and bake for an additional 15 minutes.
The bottom of the bread will have a hollow sound when tapped so show it is done.
Cover the bread in a tea towel and lightly sprinkle water on the cloth to keep the bread moist.