Rub the fish inside and out with salt and olive oil. Leave for 45 minutes before steaming the fish over boiling water for 15 minutes.
Heat the groundnut oil in a wok or frying pan. Add the chilli pepper, ginger and spring onion and stir for one minute. Add the soy sauce, vinegar, tomato purée, orange juice and sugar and cook for a further 8 minutes. Dissolve the arrowroot in 3 tablespoo