I think I first had aburi maguro in Osaka back in 1999. It was just one
of those run of the mill sushi bars in the underground complex by the
train station (near Daimaru). They recommended it and said it was
maguro tattaki. It was more like a maguro zuke, seared on the outside.

Later that summer I told one of the itamae's at a sushi restaurant I
used to frequent, and he claimed he already had that idea for o-toro,
but never really publicized it (yeah right!). So he called his creation
o-toro tattaki. Basically taking two slices, flash grilling them, then
dab some orange minced ginger, negi, and maybe a wee bit of garlic on
the top, then finally dashing some ponzu over it. The end result was
amazing and it was a big hit with the patrons. I haven't been back in a
while, but the chef sometimes comes up with these interesting
creations.

I've asked a current favorite restaurant's itamae to prepare something
similar and the results were even more amazing. The caveat is that they
charge $20 for a pair of otoro, but it is very high quality Spanish
blue-fin (and bigger pieces than the other place). Instead of throwing
it on the grill, they master the control of the searing degree by using
a creme brulee torch. This gives a slightly different flavor, but at
least the searing is more even on the outside (you can still achieve a
pink center like a medium rare steak).
The same restaurant once served lightly seared uni (in gunkan) using
the same method, and the carmelization really brought out the flavor. I
think I mentioned a while ago of another chef elsewhere doing the same
for shirako in gunkan (lightly searing it for the same effect).

Bottom line is that with aburi toro, you really have to ask for it at
least here. Some will have no clue, and those who never tried serving
it that way before might stumble. I'd rather leave it in the able hands
of 2 to 3 of my favorite places, and leave it at that :-).

Btw the creme brulee torch searing/aburi seems to work great with good
quality shiro maguro, especially bincho (plus ginger + negi + garlic +
ponzu). :-) Also fantastic with engawa (though a toaster oven can do
the same job, given the right amount of heat).