The popularity of this dish has kept it off the (dinner) menu.

I usually associate bright flavours with tuna tartare but the dressing on this one has an almost deep, complex flavour that just as well compliments the fish - almost smokey, but I couldn't put my finger on it. It was difficult to tell if it was coming from the dressing or the sesame cone but either way, it was different and outstanding in all of the tuna tartare's I've had thus far.
Definitely a signature worth trying, at least once if anyone were to go to the beautiful space of Spago.