1. What a cemita actually is — and why it's not a torta
Cemitas and tortas share the concept of a filled bread roll, but they diverge at the bread itself and at a single fresh herb that separates one from the other. A cemita's bun — which lends its name to the entire sandwich — is round, slightly sweet, eggy in texture, and topped with a blanket of white sesame seeds. Where a telera (the torta's standard bread) is neutral in flavor and designed to fade into the background, the cemita bun contributes its own sweetness and richness to every bite. The standard assembly works like this: the bun is split and warmed; one half gets a smear of chipotle en adobo; the filling — most often a thin milanesa cutlet — goes in warm; quesillo, Oaxacan string cheese, is pulled into strands and pressed against the hot meat so it begins to melt; avocado is sliced in; and a small handful of papalo goes on last, raw, so it perfumes the entire sandwich from above. That final element is what most torta traditions in Mexico City skip entirely, and it is what turns a filled bun into a cemita.