Preheat the oven to 400 degrees F. Butter a 9-inch cast iron skillet.
In a large bowl, whisk together the cornmeal, flour, baking powder, and salt.
In a standing mixer fitted with the paddle attachment, or with a hand-held electric mixer and a large bowl, combine the butter and sugar and mix until light and airy. Add the eggs one at a time, mixing well between each addition.
Add the cornmeal mixture to the butter mixture in 3 parts, alternating with the milk in 2 parts, until just combined into a thick batter. Using a rubber spatula, scrape the batter into the prepared pan and smooth the top. Bake until lightly browned and a toothpick inserted in the center comes out clean, about 30 minutes. Set aside to cool slightly before serving.