1 small shallot, minced
1/2 teaspoon finely grated fresh ginger
1/3 cup soy sauce
1/3 cup lime juice
1/2 cup minced ginger, for coating tataki
1/4 cup sesame seeds, for coating tataki
Freshly ground black pepper
Kosher salt, for the tataki
3 tablespoons peanut oil, for searing tataki
1 tablespoon lime juice, for deglazing tataki
2 cups mixed baby greens
1 medium-size, ripe avocado, peeled, pitted, quartered and sliced
12 thin slices red onion
1/2 cup cherry tomatoes, halved, or 1 medium tomato, peeled, seeded, and diced
1. Make the Ginger Soy Lime Vinaigrette: Stir together the shallot, ginger, a few grinds of pepper, soy sauce and lime juice in a small bowl. Whisking continuously, slowly drizzle in the olive oil. Set aside. When ready to serve, whisk the dressing thoroughly to recombine the ingredients.
2. If preparing the tuna sashimi-style, do not season it or cut it in any way.
3. If you plan to serve it tataki-style, on a shallow plate stir together the ginger, sesame seeds, and cracked black pepper. For the tataki, use a sharp knife to cut 1/2-inch-deep notches at regular intervals of 1/4 to 1/2 inch along the length of the tuna, to make it easier to slice after searing. Season the tuna with salt and roll it in the ginger mixture, pressing down lightly to make the coating adhere on all sides.
4. For the tataki preparation heat a sauté pan over high heat. Add the peanut oil and, when it is hot, sear the tuna on all sides, 30 seconds to 1 minute per side, turning it with tongs. Remove the tuna from the pan and set aside. Add 1 tablespoon lime juice to the pan and quickly stir and scrape to deglaze the pan deposits, then drizzle the deglazing liquid over the tuna.
5. For the sashimi preparation, simply cut the tuna crosswise into uniform slices about 1/4 to 1/3 inch thick.
6. In a bowl, toss the greens with just enough of the vinaigrette to lightly coat.
7. To serve: Mound the greens on 4 serving plates. Arrange the sashimi slices overlapping around the mounded greens; or cut the seared tuna into slices, starting at the notches you cut before cooking and arrange them overlapping around the greens. Garnish with avocado, red onion and tomato. Drizzle more of the dressing over each serving. Serve immediately.