Preheat oven to 350 degrees F. Grease and flour a 9-inch round cake pan, or you can use a 12 in. cast iron skillet.
In a large bowl, whisk the flour, baking soda, and salt. Stir in the butter with a wooden spoon. Gradually stir in the buttermilk until the dough comes together.
Turn dough onto a floured surface and knead gently a few times. You do not have to overdo it on the kneading. The dough will be somewhat sticky. Form the dough into a 6-7 in. dome shape and place it in the center of the skillet.
Cut an X into the dough with a sharp knife, about 1/2 of an inch deep. Sprinkle with coarse sea salt.
Bake for 35 minutes. Keep an eye on the top. It should turn a golden brown. It will have a thumping sound if you tap on it.
This was super easy to make, and the recipe only called for five ingredients. I was planning to serve this with our St. Patrick’s Day corned beef and cabbage dinner. The only problem is that, once we started eating it, we almost finished it off. I will probably have to make another one! It tasted great with butter and apricot jam.