Cut tomatoes into 1/4- to 1/3-inch-thick slices; place in a shallow dish. Pour buttermilk over tomatoes. Sprinkle with salt and pepper.
Combine flour and cornmeal in a shallow dish or pieplate. Dredge tomato slices in flour mixture.
Fry tomatoes, in batches, in hot oil in a large cast-iron skillet over medium heat 3 minutes on each side or until golden. Drain on paper towels. Sprinkle with salt to taste.