Preheat your oven to 425 degrees farenheit.
Place the cast-iron skillet on the eye of the stove and set for medium heat. Add the oil.
While the oil is heating, crack the egg into a small bowl and whisk with a fork. Add salt.
Add the meal and baking powder (if using) to the bowl. Mix until it has a dry paste consistency.
Add the buttermilk, in small amounts, until the mixture resembles a thick pancake batter. It should be very thick, but pourable.
Add 1/2 of the hot oil to the batter. Quickly mix that into the batter, then immediately put everything into the skillet.
Bake at 425 degrees farenheit for approximately 15 minutes. The cornbread is done when the surface has a brownish-yellow color and the cornbread sounds hollow when thumped. You can also use the toothpick test. A toothpick inserted into the center of the cornbread will come out clean if the cornbread is finished baking. Remove from the oven and immediately turn out onto a cooling rack or plate. Allow to cool until you can handle it safely, then cut in half, half again, and each quarter in half again, giving you 8 triangular slices.
Serve hot with butter.