Preparation Prepare grill for direct-heat cooking over hot charcoal (high heat for gas); see Grilling Procedure . Whisk together olive oil, sesame oil, soy sauce, vinegar, and ginger. Combine coriander seeds, white peppercorns, and kosher salt in a small bowl. Rub vegetable oil all over tuna, then coat with spice mixture, pressing gently to help it adhere. Oil grill rack, then grill tuna, covered only if using a gas grill, turning onto all sides, until seared on all sides but still very rare inside, 6 to 8 minutes total. Transfer tuna to a cutting board and cut across the grain into 8 slices. Julienne jicama using an adjustable-blade slicer fitted with 1/8-inch julienne attachment or using a knife. Toss watercress and jicama with enough dressing to coat, then season with salt and pepper. Serve tuna over salad, sprinkled with scallions. Serve remaining dressing on the side. Cooks' Note•The tuna in this recipe will not be fully cooked. •Tuna can be cooked in a lightly oiled hot grill pan over medium-high heat. •Tuna can be grilled 1 day ahead and chilled (covered once cool).
Preparation Prepare grill for direct-heat cooking over hot charcoal (high heat for gas); see Grilling Procedure . Whisk together olive oil, sesame oil, soy sauce, vinegar, and ginger. Combine coriander seeds, white peppercorns, and kosher salt in a small bowl. Rub vegetable oil all over tuna, then coat with spice mixture, pressing gently to help it adhere. Oil grill rack, then grill tuna, covered only if using a gas grill, turning onto all sides, until seared on all sides but still very rare inside, 6 to 8 minutes total. Transfer tuna to a cutting board and cut across the grain into 8 slices. Julienne jicama using an adjustable-blade slicer fitted with 1/8-inch julienne attachment or using a knife. Toss watercress and jicama with enough dressing to coat, then season with salt and pepper. Serve tuna over salad, sprinkled with scallions. Serve remaining dressing on the side. Cooks' Note•The tuna in this recipe will not be fully cooked. •Tuna can be cooked in a lightly oiled hot grill pan over medium-high heat. •Tuna can be grilled 1 day ahead and chilled (covered once cool).