Begin by thoroughly cleaning the catfish (paglilinis ng hito). Rub the fish with rock salt (asin) to remove the slime and let it sit for 5 minutes. Using a dull knife, scrape the fish gently, then rinse with calamansi juice. Perform a final salt rub and rinse with water. Cut the cleaned fish into 2-inch sections and combine with soy sauce (toyo), peppercorns (paminta), and half of the minced garlic (bawang). Allow to marinate in the refrigerator at 40°F (4°C) for 10-15 minutes.
While the fish marinates, prepare your aromatics by mincing the garlic, thinly slicing the onions (sibuyas), julienning the ginger (luya), and chopping the tomatoes (kamatis). Have all your sauce ingredients measured and ready.
Heat canola oil in a large wok or deep pan (kawali) to 350°F (175°C). Carefully fry the marinated fish sections until they achieve a golden brown color, approximately 5-7 minutes. Remove the fried fish and drain on paper towels to remove excess oil. Keep the oil hot but reduce to medium heat.
In the same pan, sauté the remaining garlic, onions, and ginger until fragrant at medium heat (350°F/175°C). Add the chopped tomatoes and cook until they become soft. Pour in the vinegar (suka) and bring to a boil for 2 minutes without stirring. Add the soy sauce, water (tubig), brown sugar (asukal), bay leaves (dahon ng laurel), star anise, and whole peppercorns.
Once the sauce is simmering, carefully add the fried catfish pieces. Reduce the heat to low (300°F/150°C) and let it simmer for 15 minutes, allowing the fish to absorb the flavors while the sauce reduces to your desired consistency. Occasionally spoon the sauce over the fish, being careful not to break the pieces.
Serve hot, garnished with fried garlic bits and chopped green onions. This dish can be stored in an airtight container in the refrigerator for up to 3 days. When reheating, use low heat in a pan with the sauce for 10-15 minutes to maintain the fish's texture.