English: Tam som-o nam pu (Thai script: ตำส้มโอน้ำปู) is a northern Thai speciality. It is a pomelo salad which uses crab extract as a flavouring. This black sauce is achieved by pounding pu na ("ricefield crabs", Somanniathelphusa) to a pulp, and then straining the juices which are then boiled until the sauce becomes as thick as molasses.