The Mercado República is a working market north of the historic centre, and the fondas — small, family-run food stalls — along its upper level are among the best-value eating in the city. Each fonda specialises in two or three dishes and cooks them well and consistently. Look for pozole rojo (a hearty hominy and pork stew finished with dried oregano and lime), gorditas potosinas (thick oval masa cakes split and filled with beans, cheese, or chicharrón), and the zachuli — a very large tamale wrapped in banana leaves that feeds a group.
The market atmosphere is genuine and there is no tourist concession in how the food is presented or priced. Arrive between noon and 2pm when everything is freshest. Point at what looks good in the pots; menus are rarely written.