Heat oil to 350° F in a large skillet.
Whisk egg and buttermilk in a small bowl. In another bowl, stir together cornmeal, flour and seasonings. Dip tomato slices in egg mixture; then dredge in cornmeal mixture, shaking off excess.
Fry tomato slices, in batches, in hot oil for 1 minute on each side; drain on paper towels. Remove any excess oil from pan.
Season catfish fillets with salt and pepper, and place in skillet. Cook for 3 minutes, flip and cook an additional 3 minutes. Remove from pan. Cut fillets in half. Place a fried tomato on the plate, and top with catfish. Repeat, ending with tomato on top. Serve with a side salad and your favorite dressing.