Preheat oven to 400 degrees F. Lightly grease a baking sheet.
In a large bowl, stir together whole wheat flour, flour, sugar, baking powder, baking soda and salt. Add buttermilk all at once, stirring with a fork to make a soft, but slightly sticky dough.
With lightly floured hands, form dough into a ball. On a lightly floured surface, knead the dough gently for 8 to 10 times. Pat the dough into a 6-inch thick round, with a slightly flattened top.
Place dough on prepared baking sheet. With a shape knife or pizza cutter, score the top in the shape of a cross or large X. Bake in preheated oven for 35 to 45 minutes. Remove from baking sheet onto a cooling rack immediately. Dust top with rice flour. Serve warm from the oven.