I never have buttermilk on hand, but I always have milk and vinegar, which is how I make this.
1 T shortening
1 C buttermilk (see below for substitute)
1 C self-rising corn flour
1/2 t salt
1 egg, beaten
Preheat the oven to 450. While it’s heating, put the shortening in a cast-iron skillet and melt it in the oven.
Meanwhile, in a large bowl, combine the buttermilk, corn flour, salt, and egg. Remove the skillet from the oven and swirl the shortening around to coat the bottom. Pour the batter into the skillet and bake until browned, about 35 minutes.
If you don’t have buttermilk, you can do the following: Put one tablespoon of vinegar or lemon juice in a measuring cup. Add milk to make one cup. Let stand for 5 minutes before using.