2½ cups all-purpose flour (divided)
1½ cups cornmeal
1 tablespoon salt
1 teaspoon black pepper
¼ teaspoon cayenne pepper
1 cup of buttermilk
1 teaspoon baking powder
½ teaspoon baking soda
2 medium green tomatoes (about 12 ounces each, seeded and sliced ¼ inch thick (for a total of 12 to 14 slices))
1½ to 2 cups vegetable oil
Place 1 cup of flour in a large shallow dish.
Whisk together the cups of flour, cornmeal, salt, black pepper, and cayenne pepper in a second large shallow dish.
In a medium bowl, combine the egg, buttermilk, baking powder, and baking soda (the mixture may bubble and foam).
Working with several slices at a time, cover tomatoes with flour and shake off excess flour from each piece.
dip tomatoes into buttermilk mixture, turn to coat and allow access to drip off.
Cover the tomato slices with the seasoned corn-flour mixture, shaking off the excess. Place tomatoes on a rack on a rimmed baking sheet. Repeat with remaining tomato slices.
Pour enough oil into a 12-inch cast-iron skillet to measure ⅓ inch deep. Heat oil over high heat until it reaches 350 degrees F, 3-4 minutes.
Carefully drop a single layer of tomato slices into the oil (be sure not to fill the pan) and lower the heat to medium. Fry until the tomatoes are golden on the first side, 2 to 2½ minutes, adjusting the heat as needed to keep the oil at 350 degrees. Gently flip the tomato slices with tongs and fry until the second side is dark golden brown, 2 to 2½ minutes more. Transfer the fried tomatoes to a paper towel-lined baking sheet and refrigerate for 1 to 2 minutes. Repeat with remaining slices, adjusting heat if necessary to keep oil at 350 degrees. Serve immediately.