Great post by Yglesias. I agree 100%. We do tend to essentialize other cultures in our efforts to seek out "authenticity" as travelers.

The peril of inauthenticity lies not in the quality of the food or the experience
but in the dilution of the communicative capacity of language. We're not
Humpty Dumpty, you know.

"I�m interested in this relationship between doing things right and doing things the way they�ve always been done"

Unfortunately, the worst offenders have no idea how to do things right nor how to do things the way they�ve always been done.

The perils of inauthenticity are very real and very prevalent.

A visitor to Madrid is likely to get more authenticity from the gazpacho or salad they get at a local McDonalds then they are from someplace offering paella.

The true bonus of going somewhere like KFC or McDonalds abroad and having one of the unique local menu variants is that you already know the 'benchmark taste' that's being adapted, you can appreciate the adaptation for what it is and learn something about local tastes through that adaptation.
On the other hand, when you eat that horrible paella mixta with peas and onions you're unlikely to even realise that you're eating something that's been adapted beyond recognition solely to fit travelers' desires - you'll learn nothing.
The irony is that promenading visitors still occasionally burping up the taste of their vile Paellador will inwardly sneer at the tourists sitting outside the McDonalds utterly convinced that it is they that have had the meaningful gastronomic experience.

But what is authenticity in this context? What is an authentic Madrid gazpacho?

Very much agreed. I don't think it is a crime to step into a McDonald's when abroad. Though it may be a crime to get the Big Mac.

That's one of the pluses of a large corporation's adaptations. The local variation won't be truly local. The variation used will be that considered the most quintessential by the entire country (in this case an Andalucian style of gazpacho made in Murcia by the Alvalle company).
There may be authentic Madrile�an gazpacho but I've never heard of it, so if I did pick out Gazpacho Madrile�o on a conventional restaurant's menu I'm just as likely to get fobbed off with an unauthentic concoction as any other visitor (my own expectation is that it would be a mixture of meat and unleavened bread in the Gazpacho Manchego style so this would be an easy expectation to anticipate and satisfy which would leave me none the wiser).