Cut lamb into small pieces.
Marinate it with oil, vinegar, tamarind and salt at room temperature for 5 hrs.
Put 2 tbsp of oil, onion, garlic and ginger in a food processor or blender and run the machine, until a fine pasty puree is formed.
Heat 1/2 cup oil in large skillet on a medium-high flame.
Add onions and saute, until they are caramel brown, stirring constantly to avoid burning.
Add cumin, mustard, turmeric, red pepper, paprika and cinnamon.
When the spices begin to sizzle and turn dark(about 15 seconds), add the lamb and bones(without the marinade).
:- Reserve the marinade.
Cook, until slightly seared for about 10 mins.
Add water to the marinade to make 2 1/2 cups of liquid.
Add it into the pan and bring to a boil.
Lower the heat and simmer, partially covered, until meat is very tender for about 30 mins.