Heat dry skillet in upper and lower thirds of oven while preheating oven to 450 degrees F.
Whisk together cornmeal, flour, baking powder, baking soda, and salt. Add egg, buttermilk, and 1/2 cup melted butter, then quickly stir together.
Remove hot skillet from oven. Divide remaining 1/4 cup melted butter between them, then divide batter between pans. Bake in upper and lower thirds of oven, switching position of pans halfway through baking, until golden and a tester inserted in center comes out clean, 15 to 20 minutes total.
Recipe courtesy of Gourmet Magazine