Slice the tomatoes into ⅓ inch slices. Place in a colander and sprinkle with salt. Let sit for 5 minutes. Rinse off the salt and pat dry with a paper towel.

In a bowl, combine the beaten egg and buttermilk and set aside.

In a pie plate or flat bowl, combine flour, cornmeal, panko, salt, pepper, garlic powder and onion powder. Mix to combine.

Dip the tomato slices into the egg mixture and then dredge in the flour mixture and place on a wire rack.

Heat the oil and butter in a cast iron skillet to about 375º. Add 3-4 slices to the hot oil, do not crowd the tomatoes. Cook on 1 side for about 1-2 minutes. Flip over with a spatula when golden brown and cook for another 1-2 minutes on the opposite side. Only flip 1 time. Remove to a wire rack and immediately sprinkle with additional salt. Allow the oil to heat back up and repeat until completed. Allow the tomatoes to cool slightly before eating.