Put the coconut, cumin and fennel seeds, coriander, red chili, turmeric and garam masala powders into a blender with 2tbsp water and grind to a paste. Set aside.
Heat the oil in the frying pan and fry the sliced onions over a moderate heat for 10 minutes.
pop the green chilies and tomatoes and saute for 5minutes. Then add the vinegar and 1cup of water and salt to taste. Simmer for 10 minutes.