We do not know. We have heard that you can soak regular prunes in tamarind paste overnight to create a substitute for Middle Eastern sour prunes, which, we have also heard, are getting harder and harder to find these days. Sour prunes are made by drying red plums, which are tangier and less sweet than the darker plum varieties that make up most of our prunes.

Sour prunes are used in a variety of dishes throughout the Middle East and beyond - from a traditional Jewish tsimmis with sour prunes and sweet potato to a Russian sour prune sauce, or an Azerbaijani lamb soup with chestnuts, quince, and sour prunes to an oh-so-nouveau duck and pistachio terrine garnished with sour prunes, which appears to have no visible link to Middle Eastern (or Central Asian) cooking.

We have also heard people compare the flavor of tamarind pulp to sour prunes, but that doesn't get us any closer to an answer for your question, either. It may be that we'll have to wait for one of our well-informed readers to help us out.