Wash the sardines and gut them (or buy them pre-prepared).
Sprinkle a good layer of sea salt on foil and place sardines on top, then sprinkle more salt over, cover and refrigerate for at least 1 hour. While you're waiting, light your barbecue and wait for it to heat up. Charcoal barbecues are ready once the coal has become embers (approximately 30-40 minutes).
Remove sardines from fridge, brush off most of the salt and place on a fish grill tray. Mix oil and juice of ½ lime and brush over the fish.
Grill on high heat on grill tray, about 4-5 minutes per side, baste with oil & lime juice. Serve with remaining oil & lime juice, season with sea salt & rainbow peppercorn.