Preheat oven to 425°.
Sprinkle cornmeal generously over the bottom of an 8" iron skillet or metal pie pan.
In a large bowl stir together dry ingredients.
Pour milk into a small bowl. Pour vinegar into milk. Do not stir. Let stand for 2 minutes.
Pour liquid combination into dry ingredients and mix together with a wooden spoon. When well combined, form into a ball. Place ball in the center of the prepared skillet and flatten ball to a 7" round.
Using a sharp knife cut a deep cross from side to side in the top of the dough.
Bake at 425° for approximately 40 minutes. Bread should be brown and hollow sounding when tapped. Remove from oven and cool slightly before cutting into wedges and serving.