First, soak the tamarind in 2 cups of hot water for 20-25 minutes.
After that, using your hands rub the soaked tamarind in water and squeeze the tamarind pulp.
Strain the pulp with a mesh strainer and keep this aside.
If you are using tamarind paste skip all of the above steps and start from the below mentioned step.
In a pan add tamarind paste along with ½ cup water.
Now add jaggery powder, dry ginger powder, black salt, cumin powder and mix everything well.
Allow it to simmer for a few minutes till the sauce starts to thicken.
Switch off the heat this will thicken further when it is cooled.
When cooled you can store it in a clean glass container in a refrigerator, and use it as required.