Preheat your oven to 375°F / 190°C.
Place the butter in an 8-inch cast-iron skillet or a square baking pan and put it in the oven to heat up while it preheats.
In a large bowl, whisk together the dry : cornmeal, all-purpose flour, baking powder, salt, and sugar.
In a separate medium bowl, whisk the egg into the buttermilk until well combined.
Carefully remove the hot skillet from the oven. Swirl the melted butter to coat the bottom and sides, then pour the excess butter into the buttermilk mixture and whisk to combine.
Pour the wet into the bowl with the dry .
Stir with a spatula until just combined—a few lumps are okay!
Do not overmix.
Pour the batter into the hot, buttered skillet and smooth the top.
Bake for 25 to 30 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean. The edges should be pulling away from the sides of the pan.
Let it cool in the pan for a few minutes before slicing.
Serve hot or warm.
Do not overmix the batter!
Stir only until the wet and dry are just combined. Overmixing develops the gluten in the flour, resulting in a tough, dense cornbread instead of a tender one.
