Preheat the oven to 400°F.
Put 1 tablespoon of the vegetable oil into a 9-inch round baking pan or cast-iron skillet. Put it in the oven to heat for at least 10 minutes.
Stir together the cornmeal, flour, baking powder, salt, and cayenne in a large mixing bowl. Add the buttermilk, the remaining 1/4 cup oil, and the egg and stir just to blend.
Pour the batter into the preheated pan. Bake until lightly golden brown, about 25 minutes. Let cool for 10 minutes before serving.
Yield: one 9-inch round bread (about 6 servings)