01 - Whisk together buttermilk and hot sauce in a shallow dish. Add catfish fillets, ensuring they're fully coated. Cover and marinate in the refrigerator for at least 15 minutes, up to 1 hour for deeper flavor.
02 - Combine cornmeal, flour, Cajun seasoning, garlic powder, paprika, salt, and black pepper in a large plate or shallow bowl. Mix thoroughly to distribute spices evenly.
03 - Pour 1 inch of vegetable oil into a deep skillet or Dutch oven. Heat to 350°F over medium-high heat. Maintain temperature throughout frying for optimal crispiness.
04 - Remove catfish from marinade, allowing excess liquid to drip off. Dredge each fillet in the cornmeal mixture, pressing gently to ensure the breading adheres completely to all sides.
05 - Fry fillets in batches to avoid overcrowding, 3–4 minutes per side, until golden brown and crispy. Transfer to a paper towel-lined plate to drain excess oil.
06 - Combine mayonnaise, chopped dill pickles, capers, lemon juice, Dijon mustard, and fresh parsley in a bowl. Mix well until fully incorporated. Season with salt and pepper to taste.
07 - Plate the fried catfish while hot, accompanied by the homemade tartar sauce on the side. Serve immediately while fillets are at their crispest.