The Tomatillo fruit is surrounded by a paper-like husk formed from the calyx. As the fruit matures, it fills the husk and can split it open by harvest. The husk turns brown, and the fruit can be any of a number of colors when ripe, including yellow, red, green, or even purple.
Tomatillos are the key ingredient in fresh and cooked Latin American green sauces. The freshness and greenness of the husk are quality criteria. Fruit should be firm and bright green, as the green color and tart flavor are the main culinary contributions of the fruit.
Even though Tomatillos are sometimes called "green tomatoes", they should not be confused with green, unripe tomatoes.