In a large bowl or pot, combine the dry ingredients (flours, salt, yeast, cranberries and walnuts. Cornmeal not included). Add the water and stir until a shaggy ball forms.
Let the dough sit at room temperature with a loose cover (I use the lid to the pot, slightly cocked so gasses can escape) for two hours. After two hours turn the dough out onto a floured surface and give it 3 or four turns (or kneads) just to make a coherent, smooth ball. Cut into two or leave as one large piece of dough. Shape into a round ball.
Place the shaped dough onto a baking sheet covered with parchment paper and sprinkled with cornmeal. Let rise for at least one hour or until double in size. At the end of the rise, preheat the oven to 450 degrees.
Using a sharp knife or a serrated bread knife, gently make a few slits across the top of the dough. Brush or spritz the dough with water and bake for about 30 minutes or until the crust is a deep golden brown. Remove from the oven and cool on a wire rack.