Melt butter in a Dutch oven or stew pot. Add the onions; cook over low heat, stirring frequently, until onions brown. Add the lamb, coriander, turmeric, cumin, and ginger. Cook, stirring frequently, for 10 minutes.
Mix in the salt, ground dried chile, yogurt, and tomatoes; cook, stirring occasionally, until mixture is dry. Add the water; cover and cook 30 minutes, or until the meat is tender. Watch carefully and add a little more boiling water if necessary. Serve with rice or chapati.