Mix theed chilli powder, cumin powder, a little sugar and black salt (to taste) to the curd and then temper only with mustard seeds in a tsp of oil. For a slight variation of the same recipe. This is my recipe for Palak raita. I tried yours and it is as good.
Spinach is one of my favorite vegetables and I lilke to thank you for posting this refreshing side dish. We had this with other Indian dishes and it replaced the raita I usually make. I doubled the spinach and used only one tablespoon of the oil.