I thought I wrote about it, and maybe I did and I just can't find the thread.
I believe Ka'an started out as part of Grupo Santanera - an operator of pretty good restaurants and clubs in the area. It seems like Santanera were trying to ride on the now widely imitated Hartwood schtick (no electricity, wood burning, going to the Valladolid market, etc.), but that they happened to have tapped chef Hugo Duran who was actually very, very serious about ancestral cooking.
Then the BPM massacre happened, Santanera operations folded, or were taken over by someone else you don't want to know about, and Ka'an was left to its own devices, operating out of a lot proudly sporting a "clausurado" sign by the municipality, 2 miles into the Sian Ka'an reserve that you have to travel at around 2mph, with an online reservation system that takes reservations when the place is closed (taking that road twice was not fun, I can tell you), but...
The food is unlike anything you've had. Clever use of fermentation and acidity (not as easy as in New Nordistan), local ingredients, and a true sense that this is what things would have tasted like before modern cooking oils, beef, etc. The beachfront setting doesn't hurt either.
Highly recommended (but note this isn't a major SP style production, even if the tableware is nice)