Clean the fish and remove the skin. Separate the flesh from the fish bones and cut the fillet into 1 inch crosswise.
Rub the fillet with calamansi juice, salt, pepper and MSG.
Before frying, coat with cornstarch then dip in beaten eggs and roll in bread crumbs.
Deep fry in a medium heat until golden brown. Set aside.
To make the sauce, in a saucepan mix thoroughly the cornstarch and sugar in 1/4 cup water.
Add in onion, garlic, cucumber, tomato, bell pepper, pineapple juice, vinegar, soy sauce, and margarine.
Cook over medium heat stirring constantly until the mixture starts to boil.
Cook for about 2 minutes more until the sauce thickens then pour over fried fish fillets.