By Ray Lampe, Dr. BBQ
Toast the buns lightly directly on the cooking grid. Transfer to serving plates. Add the griddle and grill pan to the EGG and let them heat up for 3-4 minutes. Drizzle 2 tablespoons of the oil on the hot griddle then add the sliced onions. Season lightly with some of the BBQ rub. Cook and toss the onions until caramelized. Add the butter and mix well. Cook until the butter is melted and incorporated, then transfer to a plate. Meanwhile season the fish lightly with some of the BBQ rub. Brush the hot grill pan with the remaining oil. Place the fish filets on the grill pan. Cook for 3-4 minutes and flip. Brush with BBQ sauce. Cook 2-3 more minutes and flip again. Brush with BBQ sauce. When the fish is done transfer to the buns and top with the onions and additional BBQ sauce if desired.