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.
02 - Combine cornmeal, flour, Cajun seasoning, paprika, garlic powder, salt, and black pepper in a separate shallow dish. Mix until all spices are evenly distributed throughout the coating mixture.
03 - Remove catfish from marinade, allowing excess liquid to drip off. Press each fillet firmly into the cornmeal mixture, ensuring an even, thick coating on all sides. Shake off any loose breading.
04 - Pour vegetable oil into a large skillet or deep fryer to approximately 1 inch depth. Heat to 350°F, maintaining temperature throughout frying for optimal crispiness.
05 - Cook fillets in batches without overcrowding, 3–4 minutes per side, until golden brown and fish reaches an internal temperature of 145°F. Transfer to wire rack or paper towels to drain excess oil.
06 - Mix mayonnaise, chopped pickles, capers, lemon juice, Dijon mustard, and fresh parsley in a small bowl until thoroughly combined. Season with salt and pepper to taste. Refrigerate until serving.
07 - Plate fried catfish immediately while hot and crispy. Accompany with chilled tartar sauce and fresh lemon wedges. Best enjoyed with coleslaw, french fries, or hush puppies.