Adjust oven rack to middle position and preheat over to 400 degrees.
In a large bowl, whisk together flour, cake flour, sugar, baking soda, cream of tartar, and salt.
Cut in cold butter to flour mixture, using a pastry blender, or clean hands.
Work the butter into the dry ingredients until it is completely incorporated creating a super fine crumb.
Make a well in the center of the dry ingredients.
Then add buttermilk. Using a rubber spatula or wooden spoon, mix the ingredients together by stirring from the center outward until a dough forms.
Turn out onto a lightly floured surface and pat together to form a 6 inch round.
Place dough onto parchment lined cast iron skillet or baking sheet.
Using a paring knife cut a small (x) into the top of the bread dough.
Bake for 35-40 minutes or until center is no longer doughy and the top is golden brown.
Remove from oven and brush with 1 Tablespoon of melted butter.
Slice and serve. It is great with your favorite jam or jelly!