Preheat oven to 180 degrees C. Sprinkle fish with salt. Combine onion, breadcrumbs, parsley and 30g butter then mix well. Stuff in the cavity of the fish then skewer closed with toothpicks (or sew).
Pour remaining melted butter in baking dish then set in the fish. Cover with bacon then baste well. Bake in preheated oven oven for 35-40 minutes.
Remove fish and discard any excess fat from dish. In remaining fish juices stir in the pineapple juice and cornflour then whisk well. Bring to a boil over medium-high heat, whisking continually, until gravy thickens. Serve over fish.
If you do not have tarakihi, you can use any other whole white fish such as gurnard.