Heat a Kadhai, pot or vessel, add the roughly chopped pineapple, turmeric powder and salt to taste along with 2 cups of water. Cook until the pineapple is slightly tender and the water has reduced considerably.
Meanwhile, grate / chop the 1/2 shell of coconut, add it in a mixer grinder.
Add mustard seeds, whole red chillies, green chillies, cumin and grind it into a smooth paste, using 1/4 cup of water.
Whisk the 1/2 cup of yogurt or curd and keep aside.
Now add the coconut gravy mixture to the cooked pineapples and mix everything well. Allow it to cook for a few minutes on low flame. Check and adjust salt at this stage.
Add a tbslp of jaggery and mix well.
Quickly add the whisked yogurt or curd, mix well and switch off the flame immediately. (Yogurt should not cook or boil else it will curdle and split).
Prepare for tempering by heating a small pan, add coconut oil, mustard seeds, whole red chillies and curry leaves. Once the mustard seeds crackle, pour the tempering over the gravy and serve immediately.