1Heat oven to 425°F and arrange a rack in the middle. Once oven is hot, place butter in a large cast iron skillet and place in the oven until heated through and butter is melted, about 5 minutes.
2Meanwhile, combine cornmeal, flour, baking powder, sugar, and salt in a medium bowl and whisk until evenly combined; set aside. Remove skillet from oven, pour butter into a large bowl and return skillet to oven. Add milk and eggs to butter and whisk until smooth.
3Add cornmeal mixture to milk mixture and stir until moistened through, about 20 to 30 strokes (it should resemble pancake batter). Immediately pour batter into skillet and smooth out. Bake until a toothpick inserted into the center of the bread comes out clean, about 20 minutes. Slice and serve.