Put ginger, garlic and onion into a food processor and add 1/2 cup water. Blend until fairly smooth.
Heat the oil in a wide, heavy saucepan over a medium flame. When hot, put in the cumin seeds. Stir for half a minute. Add the ginger-garlic paste. Stir and cook for about two minutes. Put in the coriander and stir a few times.Add the chopped tomatoes. Stir and cook for 2 minutes, mashing the tomato pieces with the back of a slotted spoon. Add the beans and salt and one cup of water. Bring to simmer. Cover, turn heat to low and cook for 8-10 minutes or until the beans are tender enough. Remove the cover. Add the lemon juice and lots of freshly ground pepper. Turn up the heat and boil away the remaining liquid, stirring the beans gently as you do so.
From the Dinner Co-op