Ooh, this is Rawon, an East Javan favorite!
It's beef soup with broth made from fermented Pangium seeds, which gives it a spicy taste and its signature black color. Often served with chilli paste, bean sprouts and a salted duck egg.
@Mossman Joe Thanks for commenting as I was wondering what I ate...haha! I was with @twilighter and we had a guided tour via Mariusz, the head curator of animals for Batu Secret Zoo. He's Polish and has been at the zoo for at least a decade and he insisted that we try a traditional Indonesian lunch when we finally took a break from looking at animals. The beef soup was so black that I was a bit apprehensive to try it, but the meal was delicious.