Amchoor powder
From Cookipedia
Amchoor powder (mango powder, amchur) is made from powdered green, unripe mangoes. It's use is confined chiefly to Indian cookery, where it is used as an acid flavouring in curries, soups, chutneys, marinades and as a condiment. It is particularly useful as an ingredient in marinades, having the same tenderising qualities as lemon or lime juice. However, where, for instance, three tablespoons of lemon or lime juice are required, one teaspoon of amchoor will be enough.