These batwan fruits are used as souring agents in Ilonggo cuisine.
Whereas the non-Visayans of the Philippines commonly use tamarind and even kamias and guavas to sour their sinigang, the Ilonggos use batwan.
Also spelled batuan.
Scientific name: Garcinia binucao
Batwan trees can be found all over the Western Visayas regions, particularly the two Negros provinces and Iloilo.