Preparation Place lemon juice in small bowl. Whisk in 1/2 cup olive oil, then olive puree. Season vinaigrette to taste with salt and pepper. Sprinkle tuna with salt and pepper; rub with remaining 2 tablespoons oil. Heat heavy large skillet over high heat. Add tuna to skillet; brown on all sides, turning occasionally, about 10 minutes. Transfer tuna to plate; chill 30 minutes. Thinly slice tuna crosswise, reserving any scraps. Spoon 1 tablespoon vinaigrette onto each of 6 plates. Arrange tuna slices, overlapping slightly, in circle on each plate. Spoon remaining vinaigrette over tuna. Dice any tuna scraps; place in center of circle. Sprinkle with chives.
Preparation Place lemon juice in small bowl. Whisk in 1/2 cup olive oil, then olive puree. Season vinaigrette to taste with salt and pepper. Sprinkle tuna with salt and pepper; rub with remaining 2 tablespoons oil. Heat heavy large skillet over high heat. Add tuna to skillet; brown on all sides, turning occasionally, about 10 minutes. Transfer tuna to plate; chill 30 minutes. Thinly slice tuna crosswise, reserving any scraps. Spoon 1 tablespoon vinaigrette onto each of 6 plates. Arrange tuna slices, overlapping slightly, in circle on each plate. Spoon remaining vinaigrette over tuna. Dice any tuna scraps; place in center of circle. Sprinkle with chives.