Heat oil in a pan. Add mustard seeds.Once they start splutterring,add cumin seeds ,fenugreek seeds,green chili, red chili ,curry leaves , ginger and garlic paste.Saute for a minute.
Now add the pumpkin pieces ,whole onions and onion paste.Fry them till the onions turn slight translucent.
Then add salt,turmeric powder ,jaggery and red chili powder one after the other.Mix this well.Cover it with a lid and cook on low flame for 7 minutes.
After the pumpkin and onion mix is cooked fully add grated coconut ,tomato puree and tamarind juice.
Allow the above mix to cook for five more minutes on low flame. When the stew is cooked on low flame, the sweetness of jaggery along with the sourness of the tamarind juice and the freshness of coconut enhances the taste.
Switch off the flame and garnish it with coriander leaves and sliced coconut.
Keep it covered until served . You can serve this hot with steamed rice.