Add water, sugar, and pureed pineapple to a saucepan and cook on medium heat for 3-4 minutes. Keep stirring frequently while cooking.
Add chopped pineapple and cook for another 3-4 minutes. Remove the pan from the heat and let the mixture cool down completely.
Whisk plain yogurt in a mixing bowl until creamy and smooth.
Add the cooled pineapple mixture to the bowl and mix well.
Add cumin powder, black salt, red chilli powder, and salt and mix well.
Chill the raita for 2-3 hours. Transfer it to a serving bowl and garnish it with chopped cilantro.