Pat catfish fillets dry with paper towels. Trim any ragged edges and slice thicker fillets into more even portions (about 4–6 oz each). Season both sides lightly with 0.5 tsp kosher salt and 0.25 tsp black pepper.

Make buttermilk soak

In a shallow bowl or rimmed dish, combine 1 cup buttermilk and 1 tablespoon hot sauce. Stir to combine. Submerge the fillets in the buttermilk mixture, cover, and refrigerate for 20–30 minutes (or up to 1 hour) to tenderize and flavor the fish.

Mix dry coating

In a large shallow bowl or plate, whisk together 1.5 cups all-purpose flour, 1/2 cup yellow cornmeal, 1.5 tsp kosher salt, 1 tsp black pepper, 1 tsp smoked paprika, 1/2 tsp garlic powder, 1/2 tsp onion powder and 1/4 tsp cayenne pepper until evenly combined.

Coating and Frying

Heat oil

Pour enough oil into a 10–12 inch heavy skillet (cast-iron preferred) to reach about 1/3 inch depth — approximately 1 to 1 1/2 cups depending on pan size. Heat over medium-high until oil reaches 350°F (175°C) or a pinch of dry coating sizzles immediately when dropped in. If you don't have a thermometer, heat until oil shimmers and a small piece of bread browns in about 45–60 seconds.

Dredge the fish

Working one piece at a time, remove a fillet from buttermilk allowing excess to drip off, then press both sides into the dry coating mix, ensuring an even, slightly thick crust. Shake off excess and place on a wire rack or plate. For a thicker crust, return briefly to buttermilk and coat again (double-dredge).

Fry fillets

Carefully lay coated fillets into the hot oil without overcrowding the pan (work in batches if needed). Fry 3–4 minutes per side for 1/2–3/4 inch thick fillets, or until crust is deep golden brown and internal temperature reaches 145°F (63°C). Adjust heat to maintain oil temperature between 325–350°F. Use tongs or a spatula to flip gently to avoid tearing the crust.

Drain and finish

Transfer fried fillets to a wire rack set over a sheet pan or to a paper towel–lined plate to drain for 1–2 minutes. Immediately dot each fillet with 1/2 tablespoon unsalted butter (or brush melted butter over the fish) and squeeze a little lemon juice over the top. Sprinkle with chopped parsley and an additional pinch of salt to taste.

Optional Tartar Sauce

While the fish soaks or fries, make the quick tartar: in a small bowl combine 1/4 cup mayonnaise, 1 chopped dill pickle, 1 tablespoon lemon juice, 1 tsp chopped capers, 1/4 tsp salt and 1/8 tsp black pepper. Stir and refrigerate until ready to serve. Adjust seasoning to taste.

Serve

Serve the fried catfish hot with lemon wedges and the tartar sauce on the side. Excellent with coleslaw, fries, or steamed vegetables. Leftovers keep in the refrigerator for up to 2 days; reheat in a 375°F (190°C) oven on a wire rack for 8–10 minutes to crisp the crust.