Slice each tomato horizontally into 1/2 inch thick slices. You should get about 8 pieces per tomato. Set aside.
In one shallow dish combine the flour, salt, pepper, garlic, onion powder, paprika, and cayenne pepper.
In another shallow dish add the buttermilk.
In a third dish combine the cornmeal, panko, salt, pepper, garlic, cayenne, and onion powder.
Pour vegetable oil into a large skillet so that it is about a quarter of an inch deep. Heat over medium high heat.
Once the oil is hot dredge a tomato slice through the flour mixture and shake off the excess. Dunk the tomato into the buttermilk until coated and then press into the cornmeal mixture until covered.
Place the tomato in the hot oil along with 4 or 5 other tomato slices. Cook for about 2 minutes per side or until golden brown. Remove to a paper towel lined plate.
Repeat this process with the remaining tomato slices.