Seared tuna or some tuna recipe? Please?....
Get the best cut of tuna you can, ahi tuna or whatever the fish person recommends. Ask them if it's good enough to eat it raw. You'll want around 3/4 of a pound.
Also, to make things easier, pick up some grapeseed oil. Olive oil and butter both have lower smoke points. Your pan is really hot and you don't want to fill your kitchen with smoke, so you want something with a higher smoke point, like grapeseed oil (or clarified butter).
Marinate the tuna steak in a bowl with some of the grapeseed oil, soy sauce, toasted sesame oil, some powdered lemongrass, a fair bit of pepper, maybe a bit of balsamic vinegar and some fresh squeezed lemon juice.
Get your pan really hot, add the oil. Throw in the tuna steak, let it sizzle a bit before lifting it off of the pan. You'll be able to watch it cook, as you see the red disappear (do not leave this unattended, it'll cook fast) flip it once the bottom 3/4 of the fish appears cooked ON THE OUTSIDE (it'll still be raw on the inside). Then, after you flip it and you see no more red, the tuna is seared, but you might want to let it cook for maybe a minute more, depending on how thick a piece you've got. Don't be afraid to slice it and check, you're gonna slice it anyway.
I slice it and put it over a salad (bagged leaves are fine) of mixed greens, strips of yellow & orange peppers, avocado, sliced cherry tomatoes, and paper thin slices of purple onion.