Place a 10-inch cast iron skillet in a preheated 425°F oven. Melt ¼ cup butter.
In large mixing bowl, whisk together cornmeal, flour and sugar. Whisk in buttermilk, melted butter and eggs. Set aside.
Add remaining ¼ cup butter to skillet in oven. When melted, remove from oven and swirl to completely coat bottom of pan. Pour in batter.
Reduce oven to 375°F; return skillet to oven and bake 20-25 minutes or until toothpick inserted in center comes out clean. Allow to cool 10 minutes.