Combine soy sauce, calamansi juice, minced garlic, black pepper, and sugar in a bowl. Add the pork chops and marinate for at least 30 minutes, or overnight for better flavor.
After marinating, remove the pork chops from the marinade (reserve the marinade) . Set aside for later use.
Heat the cooking oil in a pan over medium heat. Sauté the onion rings until they become soft and slightly caramelized. Set aside onion rings for garnish.
In the same pan, heat a tablespoon of cooking oil and sear the marinated pork chops. Sear each side for about 2-3 minutes or until lightly browned. Set aside.
In the same pan, heat a tablespoon of cooking oil and sauté the minced garlic and onion core from the onion rings.
Pour the reserved marinade and water into the pan. Add the pork chops back in, then cover and simmer for about 15-20 minutes or until the pork chops are tender.
Once the pork is tender top it with the sautéed onions, and serve with steamed rice.