01 - Whisk together buttermilk and hot sauce in a shallow bowl. Add catfish fillets, turning to coat thoroughly. Cover and refrigerate for at least 15 minutes, up to 1 hour, allowing flavors to penetrate the fish.
02 - Combine cornmeal, flour, Cajun seasoning, paprika, garlic powder, salt, and black pepper in another shallow dish. Mix thoroughly to ensure even distribution of spices throughout the coating.
03 - Remove catfish from marinade, allowing excess liquid to drip off. Press each fillet firmly into the cornmeal mixture, turning to coat all sides evenly. Shake gently to remove loose coating.
04 - Pour vegetable oil into a large skillet or deep fryer to a 1-inch depth. Heat oil to 350°F, maintaining consistent temperature throughout the frying process for optimal crispiness.
05 - Cook catfish in batches without overcrowding, frying 3-4 minutes per side until golden brown and thoroughly cooked. Transfer finished fillets to a wire rack or paper towels to drain excess oil.
06 - Mix mayonnaise, chopped dill pickles, capers, lemon juice, Dijon mustard, and fresh parsley in a small bowl. Stir until well combined, then season with salt and pepper to taste.
07 - Plate fried catfish while hot, accompanied by freshly prepared tartar sauce. Garnish with lemon wedges and serve immediately for best texture and flavor.