There is more to tuna than the mayo-based sandwich filler. In fact, if there is one fish that can handle a robust marinade and the fire of the grill, it would be tuna. Tuna is thick and dense, and it holds its shape while you take the time to sear it golden brown. The key is choosing which kind of tuna is best to use.
There are a number of types of tuna available, from albacore and skipjack (which are popular candidates for canning) to meatier bluefin tuna and ahi (also known as yellowfin), which are excellent fish choices for grilling. Bluefin, with its dark, meaty color and flavor, is the king of tuna -- and the priciest. Ahi is the next best option and my favorite. It's slightly less expensive, milder in flavor and paler in color than bluefin, with a deep rose hue that browns with cooking. This is the tuna you will find served raw and cut into small cubes in the Hawaiian poke bowls. Ahi is also delicious when seared and grilled.
Now, when talking about big fish, it's important to talk about health. With many big fish at the top of the food chain, such as tuna and swordfish, there will be increased amounts of mercury in the flesh. Ahi has a lower amount of mercury than bluefin. It's labeled a "good choice" to eat one serving a week by the FDA, and a "good alternative" by The Monterey Seafood Watch. (See links for further information below.)
This is my go-to recipe for searing and grilling ahi tuna. It's inspired by an Epicurious recipe I found years ago, and since then I've modified it slightly to my taste. I like to use a flat, not ridged, griddle when grilling the skewers, which provides more surface area to sear the fish. Alternatively, you can sear the skewers in a large cast iron pan over medium-high heat on the stove.
Grilled Ahi Tuna Skewers
Active Time: 30 minutes
Total Time: 30 minutes, plus marinating time
Yield: Serves 4 to 6
3 tablespoons unseasoned rice vinegar
3 tablespoons soy sauce
2 tablespoons toasted sesame oil
2 tablespoons light brown sugar or honey
1 tablespoon vegetable oil
1 tablespoon finely grated peeled fresh ginger
1 garlic clove, minced
2 teaspoons Sriracha
2 pounds ahi tuna, cut into 1- to 1 1/4-inch chunks
1 large red bell pepper, cut into 1-inch pieces
1 large yellow onion, cut into 1-inch chunks
Fresh cilantro for garnish
Whisk the marinade ingredients in a bowl to blend and to dissolve the sugar. Set aside 1/4 cup for brushing.
Place the tuna chunks in a large bowl. Pour in the marinade and stir to coat. Cover and refrigerate for 1 hour.
Thread the tuna on pre-soaked bamboo skewers, alternating with pepper and onion pieces. Lightly brush the vegetables with some of the reserved marinade. Let the skewers stand at room temperature while you prepare the grill.
Prepare the grill for direct cooking over medium heat and preheat a griddle for 10 minutes. Lightly oil the griddle. Arrange the skewers on the griddle, in batches as necessary, and cook to your desired doneness, turning to evenly color, 5 to 6 minutes for medium-rare. Transfer to a plate and brush with some of the reserved sauce. Garnish with cilantro and serve with the remaining sauce for drizzling.
For more information about fish nutrition and safety: