"Braised oxtail, or rabada, is very popular in Brazil," says Luke Burgess. "It's a dish that's deep in flavour, and fresh at the same time. The watercress adds bite and the tamarind acidity."
For tamarind liquid, dissolve 1 tsp tamarind purée in 90ml hot water. Asian celery is available from Asian greengrocers. If it's unavailable, substitute the stalks of the heart of regular celery.