It seems that up until about ten years ago, every Mexican
restaurant in Texas served a side salad of just iceberg
lettuce, tomato and onion. Apparently, as a cost reduction,
that disappeared.

It seemed incongruous that the salad dressing was 'ranch,
Italian, thousand island, etc.' I started asking the
waiters, owners or anyone in a Mexican restaurant what their
mother served on salads. It drew a lot of blank stares, but
never an answer.

If green salad was served in Mexican households, was there a
dressing?

What would be considered "authentic".