Combine all —raisins, tamarind concentrate, water, ground ginger, cayenne pepper, and salt—in a high-speed blender or food processor.
Purée the mixture until completely smooth, stopping to scrape down the sides of the container as necessary to ensure there are no lumps.
Check the consistency. If the chutney is too stiff, add more water, one tablespoon at a time, and blend again until it is thick but easily spreadable.
Use the chutney immediately, or transfer it to an airtight container and refrigerate. It will stay fresh for up to two weeks.
Adjust the flavors to your liking.
Add a touch of jaggery or maple syrup for more sweetness, or an extra pinch of cayenne for more heat.
Freeze extra chutney in an ice cube tray for perfectly portioned amounts.
Once frozen, transfer the cubes to a freezer bag for long-term storage.
