Combine the pork, calamansi or lemon juice, soy sauce, onions, garlic, and pepper in a bowl. Massage the marinade into the meat and let it sit for about 30 minutes.
Strain the marinade from the meat, onions, and garlic and set the liquid aside.
Heat 2 tablespoons of oil in a pan over medium-high heat then add the pork chops. Cook each side for about 2 to 4 minutes or until lightly browned.
Spoon out and reserve released meat juices during frying. Remove meat from pan and let it rest.
Add the remaining 1 tablespoon oil into the pan and cook the set aside onions and garlic until they're softened.
Return meat to pan plus the reserved marinade and meat juices.
Lower the heat and cover the pan to let it simmer for about 40 to 50 minutes or until meat is fork-tender and liquid is reduced.
One the liquid is reduced the meat tender, add salt and season it to your preferred taste before adding in the small onion rings.
Turn off heat and cover the pan. Let the residual heat and steam cook the onion rings slightly.