Prepare the stuffing by mixing the tomatoes, onion, calamansi juice, ginger, siling labuyo, salt and pepper in a bowl. Set it aside.
Remove the innards, gills and scales of the fish. Wash it thoroughly and rub some salt on the skin.
Slit the side of the fish and stuff the cavity with the mixture. Be careful not to overstuff the fish.
Wrap the fish with the banana leaf first, then the aluminum foil. Fold both ends securely.
Grill for about 10 to 12 minutes on each side over charcoal.
Unwrap and serve hot with your favorite dipping sauce.