The grill offers you two ways of preparing tuna. One method is to grill it over a high heat for about 4 to 5 minutes per side until it is cooked through. The other method is to grill it over a very high heat for about 1 to 2 minutes per side. The second method may scare more than a few people since it leaves most of the fish raw, but seared tuna is an Asian favorite that's becoming more and more commonplace in the U.S.
The Basics of Grilling Tuna
Tuna is a very lean fish and tends to dry out quickly on the grill. While marinating and applying oil to the fish will help, if you cook tuna beyond medium rare it will be dry. To combat this on the plate, you will want to serve grilled tuna with a sauce or some kind of salsa. Simply brushing the tuna with some oil, seasoning light with salt and pepper will give you a great piece of fish, as the topping will provide added flavor and moisture to the meal. Otherwise, you can marinade the tun; anything with a lot of acid will tend to cook the fish before it hits the grill, so the marinade you use should be pretty mild. Go with some olive oil, herbs, spice and a small amount of lemon juice or flavored vinegar.
Cooking Through vs. Searing
If you choose a piece of tuna that is about 1-inch-thick then it will grill in about 8 to 10 minutes, flipped once. This will get through to the middle, provided that your grill is good and hot.
You want to get the tuna off the grill before the surface starts to get crusty and burns. Unlike beef, lamb, or pork you do not need to let tuna rest before serving. Get it off the grill and onto the plate right away.
For the seared tuna, you want to prepare it pretty much the same way you would if you were going to grilling completely.
A light brushing of oil, some salt and pepper and you are ready to go. The big difference is that you need a very hot grill. Some gas grills simply can not produce the heat to properly sear a piece of tuna. Your best option, in this case, is to use a heavy cast iron skillet. The metal of the skillet will absorb the heat; you need to get a good sear as long as you preheat the pan. If you trust your grill to produce the heat, then go straight to the grate; otherwise, use the skillet or a good heavy griddle.
Charcoal grills will allow you to bank up the coals close the grate to get the kind of intense heat you need. To give you an idea of how hot you want it, the Food Network's Alton Brown sears his tuna on a charcoal chimney. This is like stacking up about ten layers of coals and setting the tuna about 2 inches from the blast furnace-like heat. The reason you want this kind of heat is because you will be grilling the tuna for about 90 seconds per side. Try getting a super thick cut of tuna, like a three-inch thick block, and then sear it on four sides, six if you can get it cut just right. The six-sided cube needs only about 45 seconds per side, a total of four and a half minutes. This gives you about a piece of tuna that has a fantastic seared crust all around and a heated middle.
How to Serve Grilled Tuna
Serve up seared tuna with a nice wasabi sauce or a balsamic reduction (boil balsamic vinegar until it gets thick, just do it outside because the smell will kill rocks). Either way you prepare tuna, always look for a good cut of fish. This means that the color is a deep red, but most importantly that it is even and doesn't have dark patches. Tuna is a great fish for grilling and is very unlike most any fish you have ever cooked. It is truly unique and well worth the effort, especially considering how easy it is.