A dark red, intensely dark red, food colouring and flavoring used in South American and Mexican cuisine
Particularly necessary for the cochinita pibil. Usually sold under the form of a thick red, crumbly paste in small packets produced by grinding together annatto, oregano, cumin, clove, black pepper, garlic, and salt. Colored red by the annatto seeds, it stains like nobody's business. Before use it is turned into a liquited by adding something acidic, like vinegar or lemon juice.
It is not particularly expensive, as the ingredients are not, and at any rate a little bit goes a long way.