1. With a sharp knife make a few slashes in the flesh on either side of the fish . Mix the onion powder, paprika, thyme and seasoning with the beer. Pour over the fish and rub into the slashes and cavity. Place the lime slices inside the fishes' bellies, cover with cling film and leave to marinate in the fridge for 1 hr.
2. Heat the grill to medium-high. Place the fish on a tray and grill for 15-20 mins, depending on the size, turning halfway through. Baste the fish with a little beer as it cooks. Serve with lime wedges to squeeze over.