To make cast iron skillet corn bread, combine cornmeal, flour, sugar, baking soda and powder, and salt in a mixing bowl. Stir in eggs and buttermilk to create a thick batter. Pour the batter into a 10-inch cast iron skillet coated with butter, and bake for 20 to 25 minutes.
Preheat the oven to 425 F, and add 4 tablespoons of butter to the cast iron skillet. Place the skillet in the oven to allow the butter to melt. Swirl it around to coat the entire bottom of the skillet.
To make the con bread batter, mix together 1 1/4 cup each of cornmeal and flour, 2 tablespoons of sugar, 1 1/2 teaspoons of baking powder and 1 1/4 teaspoon salt. Mix 1 egg with 1 3/4 cup buttermilk in a separate bowl, and then stir it into the cornmeal and flour mixture just until moistened.
Pour the batter slowly and carefully into the hot skillet. The batter will sizzle as it hits the butter, so take care not to get burned. Place the skillet back into the oven, and bake the corn bread until it's golden brown on the outside and firm in the middle, about 20 to 25 minutes. Cut it into wedges, and serve warm, straight from the skillet.
Use coarse stone-ground cornmeal for more flavor and texture. Southern-style corn bread calls for using bacon grease instead of butter, which also adds more flavor and gives the corn bread a crispier crust.