Preheat oven to 375°F. Add butter to a 9-inch cast-iron skillet and place in the oven while preheating. Once the butter has completely melted and browned, remove from the oven, 10-15 minutes.
6 tablespoons unsalted butter
In a large bowl, whisk together the cornmeal, flour, baking soda, baking powder, salt, and sugar. In another bowl, whisk the buttermilk and eggs. Add the wet ingredients to the dry and whisk until combined. Pour immediately into the hot skillet.
1 ¼ cups stone-ground cornmeal, 1 cup all-purpose flour, ½ teaspoon baking soda, 2 teaspoons baking powder, 1 ¾ teaspoons kosher salt, 2 teaspoons granulated sugar, 1 ½ cups buttermilk, 2 large eggs
Bake in the preheated 375°F oven until the cornbread is golden brown and a skewer inserted in the middle comes out clean, 20-25 minutes. Remove from the oven and cool for 10 minutes before slicing.