Preheat the oven to 425°F (220°C).
In a large bowl, whisk together the flour, baking soda, and salt.
Make a well in the center of the dry ingredients and pour in the buttermilk and melted butter, if using.
Gently mix the dough with your hands until it just comes together, avoiding overworking it.
Turn the dough out onto a floured surface and shape it into a round loaf.
Transfer the shaped dough to a baking sheet lined with parchment paper.
Score a deep cross on the top of the loaf with a sharp knife.
Bake for 30-40 minutes, until golden brown and hollow-sounding when tapped.
Let cool on a wire rack before slicing.