Combine first 5 ingredients in a large bowl. Combine egg, milk, and 1/2 cup melted butter; stir with a wire whisk. Add egg mixture to dry ingredients, stirring just until dry ingredients are moistened. Set aside.
Melt 2 tablespoons butter in an 8" cast-iron skillet over medium-high heat. Pour batter into skillet. Bake at 425° for 20 to 25 minutes or until a wooden pick inserted in center comes out clean.