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, to allow flavors to penetrate the fish.
02 - Combine cornmeal, flour, Cajun seasoning, paprika, garlic powder, salt, and black pepper in a separate shallow dish. Mix well to distribute spices evenly throughout the breading mixture.
03 - Remove catfish from the marinade, allowing excess liquid to drip off. Press each fillet firmly into the cornmeal mixture, turning to ensure complete coverage on all sides. Shake off any loose breading.
04 - Pour vegetable oil into a large skillet or deep fryer to a depth of approximately 1 inch. Heat the oil to 350°F, maintaining temperature throughout the cooking process for optimal crispiness.
05 - Fry catfish in batches without overcrowding the pan. Cook for 3–4 minutes per side until golden brown and the fish flakes easily with a fork. Transfer to a wire rack or paper towels to drain excess oil.
06 - Combine mayonnaise, chopped pickles, capers, lemon juice, Dijon mustard, and fresh parsley in a small bowl. Stir thoroughly until all ingredients are well incorporated. Season with salt and pepper to taste.
07 - Plate the fried catfish while hot and crispy. Accompany with the freshly prepared tartar sauce and lemon wedges. Best served immediately with traditional Southern sides like coleslaw or hush puppies.