In a large bowl, combine calamansi juice, soy sauce, onions, garlic, and peppercorns. Whisk until distributed.
Add pork and massage marinade on the meat. Marinate in the refrigerator for about 2 to 4 hours. Drain meat, reserving liquid, onions, and garlic.
In a wide, thick-bottomed pan over medium heat, heat oil. Add potatoes and cook until tender and lightly browned. Remove from pan and drain on paper towels.
Add pork and sear on all sides until lightly browned. Remove from the pan and drain on paper towels.
Remove excess oil except for about 2 tablespoons. Add the reserved onions and garlic (from the marinade) and cook until softened.
Add the reserved marinade, scraping sides and bottom of the pan to deglaze.
Add tomato sauce, water, and bay leaf. Stir to combine.
Add pork. Bring to a boil, skimming any scum that floats on top.
Lower heat, cover, and simmer until meat is fork-tender With a slotted spoon, remove and set aside.
Add liver spread to the sauce and stir to distribute.
Continue to cook until thickened. Season with salt and pepper to taste.
Slice pork into serving slices and arrange on a platter. Garnish with fried potatoes and pour sauce on top. Serve hot.