Preheat oven to 375F. Take a 12 inch cast iron skillet and melt butter over medium heat. Continue cooking butter while swirling pan to lightly coat the sides and bottom until the foam subsides and the butter turns a deep nut brown. Be careful not to burn the butter
Pour butter into a large bowl and don't clean the skillet. Whisk maple syrup into butter, then whisk in buttermilk, then eggs, then cornmeal, flour, baking powder, salt, and baking soda
Pour batter into skillet, which should still be hot. Bake until top is golden brown, toothpick emerges clean, about 30-40 min. Cool in skillet for 10 min before slicing