Cut a thin incision in the center of each beef cubes and gently insert a strip of pork fat. Set aside.
Heat the oil in a saucepan over medium heat. Cook until the potatoes and carrots are lightly browned. Remove from the pot and pat dry with paper towels.
Remove oil from the pot except for about 2 tablespoons. Add onions and garlic and cook until softened.
Add beef and cook, stirring occasionally, until lightly browned.
Cook for 2 to 3 minutes after adding the lemon or calamansi juice and soy sauce.
Pour in the tomato sauce, water, and bay leaves. Bring to a boil, scraping any scum that may rise to the surface.
Reduce the heat, cover the pan, and simmer the meat for 1 1/2 to 2 hours, or until tender. Add more water in increments of 1/2 cup if necessary if the beef starts to dry up before becoming soft.
Add potatoes and carrots and continue to cook until potatoes are tender and sauce is reduced.
Add bell peppers and continue to cook for about 1 to 2 minutes or until tender-crisp.
Season with salt and pepper to taste. Serve hot.