How to Make It
Fire up your grill to high. Away from the heat, coat the grill grate evenly with cooking spray.
In a small bowl, combine the miso, 1 tablespoon of water, and the grapeseed oil.
Rub the tuna steaks evenly with the miso paste mixture.
Refrigerate, uncovered, for 15 minutes.
Combine 1 tablespoon of water, the shallots, the sugar, and the wasabi. Toss well and let marinate at room temperature, folding occasionally as the juices release from the shallots.
Combine the lime juice, the soy sauce, and the black pepper in a large bowl.
Add the watermelon to the lime-soy mixture and toss. Let rest at room temperature until ready to serve.
Grill the steaks, until only marked, about 45 seconds. The tuna for this dish is best served ultra-rare.
On a cutting board, with your sharpest knife, cut the tuna into 3/4-inch-thick pieces against the grain.
Gently fold the tuna into the watermelon salad.
To serve, lay a bed of the tuna and watermelon salad on each of 4 plates. Scatter the wasabi shallots on top, and sprinkle evenly with the chives.
Cooking Light Mad Delicious