Take a bowl, put curd and salt. Churn to make it smooth. Next go in adding water and churning so as to get buttermilk consistency. Set aside.

Next place a pan, heat it with oil. Splutter mustard seeds, cumin seeds. Add dry red chillies, pounded garlic and few fresh curry leaves. Dust hing.
Saute.

Next add little water so that your tadka doesn't burn. Now add turmeric powder and rasam powder. Mix well.

Now keep the heat slow and gradually add the prepared buttermilk and go on stirring. Let it be on low heat for sometime.

It's ready... Enjoy dahi rasam when it has come to room temperature.The flavours combine well then.
It's so yum... you can drink it as such.
You can have it with hot steaming rice too.

If the curd is not sour add little lemon juice as because little sourness adds to the taste...