Preheat oven to 425 degrees. Line a baking sheet with parchment paper or Silpat liner, set aside.
Place flour, salt, and baking soda in a large bowl, whisk to combine.
Add enough buttermilk to make a stiff dough. Dough should be very soft, but not soggy. Add additional buttermilk if too dry.
Place dough on a lightly floured surface and shape it into a large round. Lift it up and place on the prepared baking sheet. Cut a "cross" in the top of the dough with a sharp knife about an inch deep across the entire surface to ward off evil spirits.....or to let the fairies out, whichever you prefer.
Place in preheated oven and bake for 30 to 40 minutes, until golden brown and loaf sounds hollow when tapped on the bottom when tapped with your fingers.
Remove from oven and wrap in a clean tea towel. Place the wrapped loaf on a wire rack to cool slightly. The towel traps the steam which helps to soften the crusty exterior.
Notes
Combine 1.75 cups milk (unsweetened cashew or coconut milk) with 2 teaspoons of apple cider vinegar to make non-dairy buttermilk.
Store leftover bread in an airtight container on the counter for up to 3 days.