Tamarind http://en.wikipedia.org/wiki/Tamarind grows in large pods that go from green to brown when fully ripe, (with a dry husk) and produces large seeds inside that are surrounded by a lemony, sweet, sour and fudgy flesh. Delicious as a snack, dip in a little sugar, but also wonderful to flavour sweet and savoury dishes.
You can of course buy the pods and remove the flesh yourself or you can buy ready prepared tamarind with seeds as a sticky block or without seeds as a smooth paste. Pinch off some of the flesh with seeds and add boiling water to soften. Mix well to remove all the flesh and strain the resulting water through a sieve. But I used a teaspoon of tamarind paste and softened it with a tablespoon of boiling water in a cup.