Preheat your oven to 350°
Heat skillet by placing in the hot oven while measuring out ingredients.
In a large bowl combine flour, cornmeal, sugar, salt and baking powder. Stir to combine.
In a medium bowl whisk together egg, milk and oil.
Pour egg mixture over dry ingredients. If using the optional ingredients add them now.
Stir to combine all ingredients. Do not over mix. Just fold until there are no dry spots.
Remove hot skillet from oven, place butter in pan and using a hot pad, swirl skillet by handle till butter is melted and evenly coats pan bottom and sides.
Pour cornbread batter into hot buttery pan and bake in preheated 350° oven for 30 minutes.
All ovens vary so check your cornbread for doneness after 25 minutes.
If you have any leftovers, they can be stored in a sealed plastic container at room temperature, or wrapped in plastic wrap and frozen.