Warm a little oil in a large wok or frying pan over a medium heat. Add the onions, cooking until soft, about 4 minutes. Stir in the okra then add the tomatoes and chilli, then season. Mix well and keep stirring gently, taking care not to break up the okra. Okra releases a sticky substance when cooked, but keep cooking, stirring gently – this will disappear and the tomatoes will become pulpy, about 10 minutes.
Lower heat, add ground coriander and cook for another 5 to 10 minutes. Add the water, cover and let simmer for another 4 to 5 minutes. Sprinkle with coriander and serve with basmati rice or chapati bread.
Tinned okra may not be available in your local shops. Try searching online or in specialty shops.