In a soup pot, combine water, ripe tomatoes and taro. Boil for 4-5 minutes or until taro is almost tender.
Meanwhile, in a saucepan, boil tamarind or sampaloc in water until soft. Mash tamarind (sampalok) in the liquid to extract juice then strain liquid into a bowl, Set liquid aside and discard the sampalok.
Add the panga ng tuna, finger chili and radish to the soup pot and simmer until tuna is almost cooked, about 8-10 minutes. Stir in reserved sampalok juice and season with salt. Adjust seasoning to taste.
Place kangkong and string beans or sitaw on top of the fish and simmer further until vegetables are cooked just right, about 2 -3 minutes. Serve piping hot with rice. Makes 2-4 servings