Heat a little water in a heavy bottom pan, add the chopped pineapple to it along with chilli powder, salt and turmeric. Cook till pineapple is tender but slightly firm.
While the pineapple is cooking, grind together coconut, cumin and mustard. Add a little water if required.
Add the coconut paste to the pineapple and cook further for about 7-8 minutes till the raw coconut smell is gone and the pineapple fully cooked.
Add the whisked curd and turn off the heat. Mix well and keep aside.
In a small pan, heat the oil and add the mustard seeds to it. Once they crackle, add the curry leaves and turn off the heat.
Pour over the pineapple mix and serve with steaming hot rice and dal.