Tammy I got the tuna steaks at walmart in the frozen fish section. It's a bag of three or so cut in 4ounce steaks at 140 calories each. I think you can get fresh tuna steaks at just about any fish market though you will have to go through all the hassle of weighing them and figuring the calories. Tuna is one of those fish you can cook and eat rare or med rare. the more you cook it the more it will taste like the one in the can. Just remember fresh tuna since it's not been packed in water or oil will get dry and crumble. I know that most people say ewwww to rare or med rare fish but tuna has a texture more like beef so it goes well. I guess thats why they use it in sushi. Anyhow.....
I take the steak and put some salt and crushed red pepper flakes and some Mrs. dash and put it on both sides. Then i put it in a sauté pan with some no calorie cooking spray and just cook it as done as i want it. The cool thing about fresh tuna is it's a pink color so you can watch the doneness through the meat. Once the first side is cooked about a quarter of the way through I just flip and get the other side about the same. with the cooking spray and Mrs. dash it gives it a blackening fish effect and it's good. You could just put on some fresh lemon juice or make some light tartar with some light mayo or salad dressing, dill or sweet relish, maybe some dill sprigs if you have them.
I have also made a oriental style tartar sauce with the light mayo, some soy and some grated ginger... A small amount of mustard in a sauce gives it a yummie taste as well.