Heat the bacon grease in a large skillet over medium heat. In one small bowl, stir together the flour, cornmeal and pepper. In another small bowl, whisk together the egg and milk using a fork.
Dip the tomato slices into the egg and milk, then coat with the dry mixture. Place the breaded tomato slices in the hot bacon grease. Cook until browned on each side, about 3 to 4 minutes per side. Bacon grease burns easily, so adjust your heat if you need to.