Preheat oven to 400. Grease a square baking pan. (8×8 will provide a nice thick cornbread and 9×9 will be slightly thinner.) In a large mixing bowl, stir together all the dry ingredients. In a medium bowl, whisk together melted butter (this should be slightly cooled before mixing), buttermilk, and eggs. Pour the buttermilk mixture into the cornmeal and stir until moistened. Do not over mix! Transfer to baking pan and smooth the top. Bake until a toothpick inserted in center comes out clean, about 20-25 minutes. Let cool in pan for 15 minutes before serving.