Put the pork in a bowl and season with salt and pepper. Then mix the pork until well coated with the seasoning.
Heat oil in a pan and saute garlic and onions until onions are soft. Then add in the pork and stir.
Saute the pork until slightly brown and the liquid has evaporated and also the fat renders.
Pour cooking rice wine and stir. Then add soy sauce and oyster sauce. Stir until the sauce is reduced to half.
Then add in brown sugar and calamansi juice. Stir for a minute then pour boiling water in the pan.
Cover and simmer until for and hour or until the pork is tender. Then add in the white onion rings and stir. Simmer for a minute then turn off heat. Serve and enjoy!