Clean bangus but do not scrape scales.
With a sharp knife slit the back to make an opening up to the stomach.
This can be done by the fish vendor when you buy it in the wet market, but in a supermarket you have to buy it whole and do the procedure above.
Wash the fish and sprinkle with salt. Mix onions and tomatoes together.
Season with salt and vetsin. Stuff the mixture inside the bangus (milkfish).
Rub the fish with 2 tbps. vegetable oil before grilling to enhance flavor.
Wrap bangus in wilted banana leaves.
Grill on hot charcoal for 1/2 hour turning the fish on the other side to avoid burning the skin.