Preheat oven to 450 degrees F (232 degrees C).
Into a mixing bowl, add All-Purpose Flour (1 cup), Cornmeal (1 cup), Granulated Sugar (1/4 cup), Baking Powder (1 tablespoon), and Salt (1 teaspoon). Whisk to combine.
Add Buttermilk (1 cup), Egg (1), and Vegetable Oil (1/4 cup). Whisk until smooth.
Transfer batter to a greased cast-iron pan. Smooth the top.
Bake for 20-25 minutes.
Spread the top of the cornbread with Butter (to taste). Slice and serve.