Preheat oven to 400 degrees F and butter a 10 inch cast iron skillet (or similar baking dish).
In one bowl, whisk together the flour, salt, baking soda and sugar.
In another bowl, whisk together the buttermilk, egg and melted butter.
Pour liquid mixture into flour mixture. Use a rubber spatula to mix into a shaggy dough.
If dough is sticky, sprinkle with a little flour, shape into a ball with your hands.
Transfer dough ball to prepared skillet. Use a knife to score an X in the top of the bread loaf (this will help the center bake).
Bake for 35-40 minutes, until loaf is golden. To test for doneness, tap the bottom of the loaf - it should sound hollow. Allow to cool slightly before slicing.