MW, it's a Mexican soup madewith beef stomach in a clear broth or with a red chili base. Usually, lime, chopped onions, and chopped cilantro are added, as well as crushed oregano and crushed red chili peppers.
Menudo is usually eaten with tortillas or other breads, such as bolillo. It is often chilled and reheated, which results in a more concentrated flavor. The popularity of menudo in Mexico is such that Mexico is a major export market for stomach tripe from US and Canadian beef producers