Skillet Cornbread

1¼ cups yellow cornmeal
1¼ cups all-purpose flour
2 tablespoons granulated sugar
1½ teaspoons baking powder
½ teaspoon baking soda
1¼ teaspoons kosher salt
1¾ cups buttermilk
1 egg...
4 tablespoons unsalted butter, cut into 4 pieces

Preheat oven to 425 degrees F.
In a medium bowl, whisk together the cornmeal, flour, sugar, baking powder, baking soda and salt. In a large measuring cup, whisk together the buttermilk and egg. Pour the buttermilk mixture into the dry ingredients and, using a rubber spatula or large wooden spoon, stir the batter together until completely combined.
Put the butter in a 10-inch cast iron skillet and place the pan in the oven until the butter is melted, about 3 to 5 minutes. Remove the skillet from the oven, swirl the butter around to coat the bottom and sides, then pour the batter into the pan. Smooth the top and bake until a skewer inserted in the middle comes out clean, about 20 to 25 minutes.