Preheat oven to 400 degrees.
Add the cornmeal, flour, baking powder, sugar, and salt to a mixing bowl. Stir to combine.
Next, add in the eggs, 1/4 cup melted butter, and buttermilk. Stir to combine.
Be sure not to over-mix the batter. Over-mixing will lead to large cracks in the crust and a lot of crumble. Only mix well enough to combine the ingredients.
Fold in the blueberries. (Optional: You can reserve some blueberries to press into the top of the cornbread batter after the batter has baked for 10 minutes).
Place a 10 inch cast iron skillet on medium heat. Add 2 tablespoons of butter. Allow it to melt and then grease the entire skillet including the edges.Alternatively, You can use any baking dish or skillet you wish that is oven safe. While the skillet is hot, pour the mixture into the cast iron skillet.
Bake for 10 minutes. Add the reserved blueberries to the top of the cornbread. If you add them to the fully wet batter, they will sink into the cornbread and won't stay on top.
Bake for an additional 15 minutes or until a toothpick can be inserted and return clean.
Allow the cornbread to cool for at least 20 minutes prior to slicing.