Make a small slit in the center of each beef cube and carefully insert a strip of pork fat into the opening. Set aside once all pieces are larded.

Heat oil in a large heavy-bottomed pot over medium heat. Fry the potatoes and carrots until their edges turn golden. Remove them from the pot and drain on paper towels.

Pour off excess oil, leaving about 2 tablespoons in the pot. Sauté the chopped onions and minced garlic until fragrant and lightly caramelized. Add the beef pieces and cook, stirring occasionally, until evenly browned on all sides.

Pour in the soy sauce and lemon or calamansi juice, allowing the flavors to soak into the meat as it simmers gently for 2 to 3 minutes. Add the tomato sauce, water, and bay leaves. Bring to a boil, then skim off any foam that rises to the surface.

Reduce the heat to low, cover the pot, and let the mixture cook slowly for about 1½ to 2 hours, or until the beef becomes fork-tender. If the sauce thickens too quickly before the meat softens, add more water in small amounts as needed.

Return the fried potatoes and carrots to the pot and continue to simmer until they are tender and the sauce has slightly thickened. Add the red and green bell peppers, stirring them in gently, and cook for another 1 to 2 minutes until just tender but still crisp.

Season with salt and freshly ground pepper to taste. Serve warm with steamed rice and enjoy this hearty, flavorful Filipino classic.