Coat the inside of your cast iron skillet with the oil, making sure to get up the sides.
Put your skillet into the oven, then preheat to 450 degrees.
In a large bowl, mix the cornmeal, flour, salt, pepper, and baking powder. Stir to combine.
Make a well in the middle of your dry ingredients. Crack the egg into the well, whisking it to break up the yolk.
Add the buttermilk to the well and stir to thoroughly combine all ingredients.
Gently fold in the cheese and scallions.
Carefully remove your skillet from the oven, then add your batter. Smooth it out with a spoon to make sure it reaches the edges of the skillet.
Bake at 450 degrees for 20 minutes. If you use a casserole or muffin tin, you may need to adjust the time.
Test for doneness by inserting a toothpick into the middle of the cornbread and pulling it out. The toothpick should be warm but clean.
Allow your cornbread to cool for 10 minutes before serving.