Grilled Tuna with Herbed Aioli

Ingredients
Dessert:
 * A lemon tart from the bakery.
 * 1/4 cup olive oil
 * 2 tablespoons red wine vinegar
 * 2 tablespoons chopped fresh basil
 * 2 teaspoons chopped fresh thyme
 * 2 teaspoons dried tarragon
 * 2 large garlic cloves, finely chopped
 * 1/3 cup mayonnaise
 * 4 7-ounce tuna steaks (each about 1 inch thick)

Directions

 * 1) Whisk together first 6 ingredients in shallow dish for marinade. Place mayonnaise in separate small bowl. Whisk in 1 1/2 tablespoons marinade. Set aioli aside.
 * 2) Sprinkle fish with salt and pepper. Place fish in marinade in dish, turning to coat evenly. Marinate 1 hour at room temperature, turning fish occasionally.
 * 3) Oil grill rack. Prepare barbecue (medium-high heat). Grill fish to desired doneness, about 3 minutes per side for medium. Top fish with aioli and serve.