Fresh Tuna?
I personally do not like raw or rare fish. I like to BBQ my Tuna steaks. It is so good when fresh. Do you know what kind of Tuna? My fav is Albacore. Rinse off the tuna under running water, and pat dry with paper towels,. before doing the following:
I either use a good Italian Salad dressing, or a touch of Olive Oil, some crushed Garlic and some salt and pepper. I marinate for 5-10 mins and then put on a hot grill. You could cook in a grill pan on the stove, but I find I enjoy the BBG Grill flavor and no fish smell in the house.
You could also cook under a broiler, similar times. as the grill times below. If you like it rare, the searing method is one many enjoy.
You could either slice into 2 1" steaks, and cook probably 2-3 mins/side, or at 2" thick it would be a longer time. If 2" thinck probably 4-5 mins/side. Fish does continue to cook when you take it off the grill. When you touch it should be firm. You could check by cutting in to see if done. If not cook a few mins longer