Soak tamarind in some water for about 15 mins. Extract it's thick juice and discard the residue.
Method
Cook pumpkin cubes adding a cup of water, turmeric powder, jaggery and a strand of curry leaves.
When the pumpkin cubes are soft, add tamarind extract and only one teaspoon of salt to it. The salt added now is just for the pumpkin cubes to absorb. Meanwhile grind coconut and Udupi sambar powder finely adding little water.
Now add the ground coconut masala to pumpkin curry. Also add remaining salt and water as per the consistency. Mix well.
Heat a seasoning pan adding all the seasoning ingredients in the order mentioned, when the mustard seeds splutter and split black gram turns slightly brown, temper the sweet pumpkin curry. Sweet pumpkin coconut curry is ready. Serve it with hot steamed rice.
Note
Make sure the sweet pumpkin cubes are cooked well before adding tamarind. Some varieties of pumpkin will not get cooked in tamarind.
The curry should not be too thin nor too thick. Add water accordingly.
You can reduce grated coconut to half cup, in that case add 2 tsp of cooked toor dal. It is equally good.