Preheat your BBQ to 500F. Make sure the grills are clean and that you greased them with oil or cooking spray. Blend the salt and pepper. Cut the lemon in half. Rub olive oil all over the fish. Season both sides of the fish well with salt and pepper mix. Don’t be shy, the salt combined with the hot grill is what will help your skin not stick to the grill when cooking. When your BBQ is to temp place fish down on one side and leave it. Don’t touch it. Place half a lemon on the BBQ to grill. Close the BBQ and let cook for four minutes.
Lift cover of the BBQ and remove grilled lemon. Using a large metal spatula you should be able to start to peel the fish off the grill easily. If you see any pull keep on the grill for another couple minutes or so until the grill marks allow for the fish to be easily flipped without ruining the integrity of the skin. Gently flip the fish, add your citrus slices to the grill and cook for another six minutes in a closed BBQ.
Meanwhile, mix all of the chimichurri ingredients in a bowl. When fish is cooked and citrus is nicely grilled, remove from the BBQ to plate. Place the grilled citrus down on a platter, place the grilled fish on top, then add arugula that has been tossed with olive oil and salt, top with chimichurri sauce.