Pangium Edule
One condition in consuming kluwek: soaked for a long time and then boiled. This is because kluwek contains cyanide which is toxic and makes the consumer drunk if consumed raw.
If you eat rawon or konro soup, that's where kluwek is used. These spices are indeed able to give a black color to the dish. However, in Sunda it is usually processed into stir-fried tablets. Equally delicious!