Combine tomato, onion, salt, ground black pepper, and lemon juice in a bowl then mix well.
Stuff the mixture inside the cavity of the tilapia. Note: do not overstuff the fish.
Meanwhile, combine oil with 1 teaspoon of salt and mix.
Brush the oil and salt mixture on the exterior part of the tilapia. Note: The salt adds more taste while the oil prevents the skin to stick on the foil.
Wrap the tilapia in aluminum foil then secure the sides.
Grill the wrapped fish for about 12 minutes per side.
Remove from the grill and transfer to a serving plate.
Serve with ensaladang talong
and steamed rice.