Melt the butter in a bowl or plate large enough to hold the tuna steak Place tuna steak in bowl, coating both sides with butter Sprinkle half of cajun seasoning on each side of steak For an extra spicy treat, add black pepper.
I recommend cooking this outdoors on your grill.
Cooking indoors will generate excessive smoke.
Heat your grill to the highest possible temperature Turn off burners (to avoid flame up) then immediately add steak Cook for 2 minutes on first side Flip and cook on other side for 1 minute.
(The steak will be very pink inside - yum!) Remove and serve immediately as it will cool quickly.
I recommend serving over garlic mashed potatoes with either wasabi mustard or wasabi mustard/mayo mix.