1. To make cornbread, first preheat the oven to 450 degrees. Place 1/3 cup butter in a 10-inch cast-iron skillet, and place in the oven for about 5 minutes or until the butter melts.
2. Combine self-rising cornmeal, a large egg, 1 tablespoon of sugar and buttermilk in a bowl, and stir well. The batter should be thin and pourable. If it seems too thick, add a little more buttermilk.
3. Remove the skillet from the oven, and tilt it so that the butter completely coats the bottom of the pan.
4. Pour the batter into the hot skillet. Pouring the batter into a hot, buttered skillet will give the cornbread a crispy exterior. Bake at 425 degrees for 25 minutes or until lightly browned.