01 - Whisk together buttermilk and hot sauce in a shallow dish. Add catfish fillets, ensuring they're fully coated. Cover and refrigerate for at least 15 minutes, up to 1 hour for deeper flavor penetration.
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. Press each fillet firmly into the cornmeal mixture, turning to coat both sides evenly. Shake off any loose coating.
05 - Place fillets in hot oil without overcrowding. Fry 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 parsley in a medium bowl. Mix well and season with salt and pepper to taste.
07 - Arrange fried catfish on a serving platter. Serve immediately with tartar sauce on the side for dipping.