Marinate liver slices in soy sauce, salt, MSG and calamansi juice for at least half an hour.
Saute onions for 4 to 5 minutes in medium fire then transfer to a serving dish.
Drain the liver and save the marinade for later use.
Then on the skillet where you sauteed the onions, fry the liver on both sides until brown but don't overcook so it won't become too tough.
Then transfer the liver on the serving dish where you put the onions and put the onions on top.
Then pour the marinade in the skillet and simmer for a few minutes.
Season with salt and pepper then pour over liver and onions. Serve hot.