omatillos are small fruits (used as a vegetable) enclosed in a husk. The fruit resembles a small unripe tomato and is usually green or yellow. The yellow color indicates ripeness, but tomatillos are most often used when they are still green. Green tomatillos are firmer and easier to slice. The husk that holds the fruit is paper-like and is light brown. The flesh is slightly acidic with a hint of lemon. Tomatillos belong to the same family as tomatoes.the Aztecs first grew tomatillos as far back as 800 B.C. and they have been popular in Mexico and other Latin American countries for many years. In the US, they are mainly grown in Texas.