Clean the fish and pat dry. Rub the seasoning both inside the belly and on the outside of the fish to coat evenly. Place green onion and onion inside the fish for extra aroma while grilling.

Wrap the fish tightly in aluminum foil and grill on a rack. The fish cooks quickly, and the foil helps retain heat so the fish stays moist and doesn't dry out. This method is great for serving the fish with rice noodles and salad, dipped in fish sauce, as it keeps the fish sweet and flavorful.