Preheat your oven to 425-degrees. Grease a Dutch oven and preheat it in the 425 degree oven for about 15 minutes, while you prepare the dough.
In a large bowl, sift together the flour, baking soda and salt. Make a well in the center and slowly pour in the buttermilk, incorporating it into the dry ingredients with a wooden spoon a little at a time.
Once you have it all mixed together into sticky dough, turn it out onto a floured cutting board and knead lightly (too much kneading will make the gas escape).
Form the dough into a ball and flatten slightly into a disc shape. Dip a sharp knife in flour and cut an X mark across the top of the dough.
Place the dough into the preheated Dutch oven, cover with the lid and bake for 30 minutes.