That sounds amazing!Honestly, my favorite way to do tuna is steaks. Take spinach, feta cheese, a little lemon zest, season and quickly fry in a skillet until the spinach has reduced in volume. Take 2 inch thick tuna steaks and cut a pocket on one side, stuff with the feta spinach mix, rub the steaks down with some lemon juice and season with salt and pepper. Toss them on the grill and grill 'em up. Oh man. That's the stuff!
edit to add; come to think of it, I think I do this with swordfish steak too.