Take a heavy bottomed vessel and drop in the chopped pumpkin pieces along with tamarind paste, a tsp of salt, a tsp of chilly powder, jaggery and turmeric powder.
Add enough water to cover the pieces and cook closed. Pumpkin gets cooked very soon, keep an eye on it.
Remove one piece after 5 mins and check if the skin is cooked, if its still hard then cook for another 3 mins. Once its just cooked and still in shape, remove from flame and filter the water into a fresh bowl. ( you can use the spiced water to make vatha kozhambu).
Now take a frying pan and add a tsp of oil and splutter mustard seeds. Add the cooked pumpkin pieces and saute for few mins until the water is absorbed.
Now add little salt, chilly powder and sugar to it and saute for few more mins.
Serve it with curd rice or ghee rice. It does go well with chapathi too
Do not remove the skin of the pumpkin. If you remove them, there is a chance that it gets over cooked and looses shape. The skin would get cooked well and will add taste to the dish.
Reserve the tamarind spiced water after cooking the pumpkins for making vatha kozhambu or simply add it to sambar.
Taste the cooked pumpkin and then add more salt and chilly powder accordingly.
Adding sugar makes it different, juicy and tasty. Do not skip it.