In San Andrés Tuxtla, we were treated to a magnificent luncheon at La Caperucita, a magnet for good eating in the Tuxtlas area. (The restaurant’s name refers to the fairy tale of Little Red Riding Hood, “Caperucita Roja,” which is also the brand name of a popular cheese.) Elodia Guevara Chávez and Juan Pablo Chávez Guevara, the mother-and-son team who built up the restaurant from its humble beginnings as a hamburger cart, pulled out all the stops to welcome us and introduce