Preheat the oven to 450 degrees F. Place a heavy-duty baking pan sprayed with nonstick spray in the oven to heat.
Mix together the melted butter, Dijon and dill in a pie plate. In another pie plate, combine the panko, cayenne and some salt and pepper. Dredge the fish through the melted butter mixture and then through the panko. Place on the hot sheet trays in the oven and bake until cooked through and lightly golden, 12 to 15 minutes.
Assemble the sandwich by slathering the toasted split roll with Tartar Sauce, topping with the breaded fish fillet and adding the tomato slices and shredded lettuce.
Mix the mayonnaise, relish, dill, mustard and hot sauce together in a small bowl. Cover with plastic wrap and refrigerate 1 hour before serving.