Preheat the oven to 375°
Butter your cast iron.
In a mixing bowl, combine flour, corn meal, sugar, salt and baking powder. Whisk to combine.
In another bowl, mix the milk, oil, egg and vanilla until well blended.
Now add the dry to the wet ingridients and stir to combine.
Once the batter is well blended, add the blueberries and gently fold in with a spatula. Make sure not to over mix.
Pour the batter into the buttered cast iron and bake in the oven for 25-30 minutes, until the center is set. The skillet will be extremely hot at this point, so let the cake cool for at least 15 minutes before slicing. Serve and enjoy!