In a bowl mix all of the seasonings for the catfish. Coat each piece of fish in the spice blend and allow to set at room temperature for 20 minutes. I would make the tartar sauce while the fish is resting.
Heat the oil in a cast iron pan over medium high heat until it just begins to smoke. Gently add the fillets to the pan and cook until a dark crust forms, about 4 minutes. Flip and fry on the other side until cooked through. Remove from heat and let rest for 5 minutes.
In a medium bowl, combine all of the tartar sauce ingredients and season t taste with salt and pepper.
Cut each piece of fish in half crosswise. Split the bread in half lengthwise and slather each top and bottom with the sauce. Layer lettuce and tomato and then top with fish. Sprinkle some fresh lemon juice over the fish and serve.