Chop the onions, coriander, chillies and garlic finely. Dice the tomatoes and blend them with the ginger to a coarse paste in a food processor. Add all the ingredients to the the flour and stir well. Add water so that the consistency of the mixture is slightly thinner than yoghurt (make sure that there are no "knots" in the batter).

Heat a non stick flat frying pan on medium to high heat, and spread the batter till it forms a fairly thin pancake. Apply vegetable oil on the sides so that the pancake comes off easily and flip over after about 2 minutes or so (it should be browned on the cooked side, and shouldn't break).

Serve with ketchup or use as a sandwich filling...