In a bowl, combine pork, vinegar, soy sauce, and pineapple juice. Marinate in the refrigerator for about 30 minutes. Drain meat from marinade, reserving liquid.
In a wide pot over medium heat, heat oil. Add onions and garlic and cook, stirring occasionally, until aromatic.
Add pork belly and cook, stirring occasionally, until lightly browned.
Add reserved marinade and bring to a boil without stirring for about 2 to 3 minutes. Add water.
Add peppercorns, bay leaf, tausi, pineapple chunks, and banana blossoms. Stir to combine.
Lower heat, cover, and simmer until pork is fork-tender.
Add brown sugar and stir until dissolved. Season with salt to taste.
Continue cooking to reduce the sauce reduced to desired consistency.