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 limp.
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 peppercorns and bay leaf,
Add black beans, pineapple chunks, banana blossoms. Stir to combine.
Lower heat, cover, and simmer until pork is tender.
Add brown sugar and stir until dissolved. Season with salt to taste. Continue to cook until liquid is reduced and begins to render fat. Serve hot.