1.To make papaya salsa, combine ingredients in a medium bowl. Cover; refrigerate until ready to serve.
2.Juice limes; reserve ¼ cup (60ml) of the juice. Cut juiced lime halves in half and reserve. Whisk 2 tablespoons of the reserved juice with fish sauce, sugar and onions in a small jug. Set dressing aside.
3.Briefly rinse the fish inside and out with cold running water. Pat dry with absorbent paper. Make two long cuts, about 1cm (½-inch) deep, into the thickest part of the flesh on each side of the fish. Drizzle fish with remaining lime juice. Place the reserved lime quarters and coriander sprigs into the cavity of the fish.
4.Spray the inside of a fish grill with cooking oil. Place the fish in the grill; close the grill.
5.Heat a barbecue grill plate until hot. Place fish on barbecue and cook over low heat for 8 minutes on each side, turning only once. To check if it’s cooked, use a fork or knife to gently separate the flesh at the thickest part, where it has been scored. If it’s white to the bone, it’s done.
6.Carefully transfer the fish to a platter; drizzle with dressing. Serve with salsa and, if you like, steamed jasmine rice.
You can make a coriander sauce by omitting the papaya in the salsa and increasing the coriander to 1 cup finely chopped leaves.Note