Wash the fish fillet and make sure all the bones are out. Rub the fish all over with the cut lemons.
Cover the fish with a liberal coating of two parts Creole seasoning to one part salt. Put on as much as will stick to the fish. Let the fish sit with the seasoning in place while you prepare the grill.
Heat a charcoal or wood grill (or gas, if you must) until very hot, with the heat source about five inches from the grill surface.
Place the fish on the grill and grill for about four minutes. Turn and continue to grill, turning ever four minutes or so. The exterior will get very dark, but it will not burn. The fish is done when you poke a kitchen fork into the center and it comes out warm to the touch of your lips. This will take 20-30 minutes, depending on the size of the fillet.
After removing from the grill, let the fish sit on the cutting board for about three minutes before cutting serving-size portions across the fillet. To dress this up into something elegant, you can make a beurre blanc sauce, preferably with more lemon than usual.