• 1/2 cup chopped mixed-olive tapenade
• 1/2 cup chopped red onion
• 1/2 cup chopped fresh basil
• 5 tablespoons extra-virgin olive oil plus additional for brushing
• 1/4 cup white balsamic vinegar
• 2 teaspoons finely grated lemon peel
• 8 1/2-inch-thick diagonal baguette slices
• 4 6-ounce ahi tuna steaks (each about 3/4 to 1 inch thick)
• 4 cups (packed) baby arugula

Mix tapenade, onion, basil, 5 tablespoons oil, vinegar, and lemon peel in medium bowl; season with salt and pepper.

Brush baguette slices and tuna on both sides with oil. Sprinkle tuna with salt and pepper. Heat large nonstick skillet over medium-high heat. Add baguette slices; toast until golden, 3 to 4 minutes per side. Transfer to plate. Add tuna to same skillet; cook to desired doneness, 1 to 2 minutes per side for medium-rare.

Divide arugula among 4 plates. Cut tuna into slices; arrange atop arugula. Spoon tapenade vinaigrette over tuna. Place 2 baguette slices alongside each and serve.