Preheat oven to 425°F.
Lightly grease a 9-inch cast iron skillet (or cake pan).
In a large bowl, mix flour, cornmeal, salt, and baking soda.
Stir in yogurt until a shaggy dough forms.
Knead just until a ball forms—if dry bits remain, add a tablespoon of water.
Flatten slightly and place in the pan.
Cut a deep "X" into the top.
Brush with egg wash and sprinkle with black pepper.
Cover loosely with foil and bake for 30 minutes.
Remove foil and bake another 10-12 minutes until golden brown.
Cool for 20 minutes before slicing.
