
Rinse beef ribs and drain well.
In a large pot over medium heat, heat oil. Add onions and garlic and cook until softened.
Add beef spare ribs and cook, stirring occasionally, until lightly browned.
Add tomatoes and cook, mashing with the back of spoon, until softened and release juice.
Add fish sauce and continue to cook for about 1 to 2 minutes.
Add water and bring to a boil, skimming scum that floats on top. Lower heat, cover, and cook for about 50 to 60 minutes or until meat is fork-tender. Add more water in 1/2 cup increments as needed to maintain about 5 cups.
Add potatoes and cook for about 7 to 10 minutes or until tender.
Add pechay and cook for about 2 to 3 minutes or until tender yet crisp.
Season with salt and pepper to taste. Serve hot.