Step 1

Preheat oven to 400 degrees F.

Step 2

Whisk buttermilk, egg and 3 tablespoons melted butter in a medium bowl.

Step 3

Place flour, baking powder, baking soda and salt in a stand mixer fitted with paddle attachment. Mix on low speed to combine. Increase speed to medium and slowly add the buttermilk mixture until a soft dough forms. Let the dough rest for 10 minutes.

Step 4

Brush the remaining 1 tablespoon butter over the base and partway up the sides of an 8-inch cast-iron skillet. Dust hands with flour and form the dough into a ball. Press the dough into the prepared pan. Use a sharp knife to score a deep "X" in the top of the dough.

Step 5

Bake until lightly browned and hollow-sounding when tapped on the bottom, 30 to 40 minutes. Remove from the pan and let cool on a rack for at least 30 minutes.