Get yourself some tuna steaks, the fresher the better. But, if you're like us and no longer live at a walking distance from the sea, I heard from a reputable source (the internet, of course!) that the frozen ahi tuna steaks from costco were a good deal, and.. yes, they are.. in fact, they're the just about the only thing from there that I regret not being able to buy after our membership expired. Alas, ~12 steaks for 17 bucks was great.
I've been asked this before and yes, it says steak, so cook it like one; although it not being completely fresh I'd go to just before the well done state before taking it away from the fire just to be safe. And since you're firing up a hot pan and putting it in the oven afterwards, make it a one-pan meal and cook your vegetables in there as well.