In Mexico City, asking for a quesadilla doesn't guarantee cheese — many market stalls treat 'quesadilla' as just the folded masa shape, and you have to specifically ask for one 'con queso' to actually get cheese inside.
Fresh corn masa is patted into a disc, folded around a filling like squash blossom, huitlacoche, mushroom, or cheese, and griddled or fried until crisp. Market stalls across Mexico City cook them to order, and the running debate over whether cheese should be assumed has become a local running joke.