Begin by cutting pork belly into 1-inch cubes (Hatiin ang liempo ng 1-pulgadang sukat). Prepare all vegetables and aromatics: chop tomatoes and onions, mince garlic, and chop chilies. Allow ingredients to reach room temperature.
Heat oil in a large heavy-bottom pan over medium heat (180°C/350°F). Add pork cubes and brown for 8-10 minutes (Igisa ang liempo hanggang maging brown), ensuring internal temperature reaches 145°F (63°C).
Add onions and garlic, sauté until translucent, about 3-4 minutes (Igisa ang sibuyas at bawang hanggang malabo). Add shrimp paste and cook for 1-2 minutes until fragrant (Idagdag ang bagoong at lutuin hanggang mabango). Add tomatoes and cook until softened, about 5 minutes (Idagdag ang kamatis at lutuin hanggang lumambot).
Pour in vinegar and do not stir for 2-4 minutes to let acids cook off (Ibuhos ang suka at huwag haluin). Add water and chili peppers. Reduce heat to low (160°C/320°F) and simmer covered for 45 minutes or until pork is tender (Pakuluan ng takip hanggang lumambot ang karne).
Season with salt, pepper, and sugar to taste (Timplahan ng asin, paminta, at asukal). The sauce should be reduced and slightly thick. Ensure internal temperature of pork reaches 165°F/74°C (Siguraduhin na umabot sa 165°F/74°C ang init sa loob ng karne).
Let rest for 5 minutes before serving with hot steamed rice (Palamigin ng 5 minuto bago ihain kasama ng mainit na kanin).
For reheating, ensure temperature reaches 165°F/74°C throughout (Kapag iinitin, siguraduhing umabot sa 165°F/74°C ang init sa loob).