Guajillo chiles
A dried, deep red Mexican chile with smooth, glossy skin, mild to medium hot, fruity and slightly tart.
Guajillo chiles are the dried form of the mirasol chile, roughly finger-length, slender and a deep, glossy red. They taste fruity, slightly tart and somewhat berry-like, with mild to medium heat, and contribute colour and depth to sauces, marinades and soups rather than fire. They are usually seeded, briefly toasted in a dry pan, soaked and puréed; the skin is fairly tough, so the paste is often pushed through a sieve. In North America they are common in the Latin section of many supermarkets; in German-speaking countries they are found in Latin American grocers and through mail order, occasionally in well-stocked Asian or delicatessen shops. Good pods are still pliable rather than brittle.
Substitute:
The closest match is dried New Mexico or California chiles, which are similarly mild and red but less tart and complex; outside North America they are just as hard to find. Sweet paprika with a pinch of chile flakes matches the colour but not the fruity acidity or the body of soaked, puréed pods, so the dish turns out flatter.