• 3/4 cup reduced-fat mayonnaise
  • 1/4 cup fresh tarragon , chopped
  • 4 teaspoons tarragon vinegar
  • 2 boneless skinless chicken breast halves
  • 3 tablespoons olive oil
  • 6 garlic cloves , minced
  • 3 medium zucchini , trimmed, cut lengthwise into 1/3-inch-thick slices
  • 1 large red onion , cut into 1/3-inch -thick slices
  • 4 kaiser rolls , split horizontally
  • 8 slices tomatoes
  • 1 Blend first 3 ingredients in bowl; season mayonnaise with salt and pepper.
  • 2 Using meat mallet, flatten chicken breast halves in plastic bag to 1/2-inch thickness; cut chicken crosswise in half. Place on sheet of foil. Brush chicken with 1 tablespoon oil; sprinkle with half of garlic, then salt and pepper.
  • 3 Place zucchini and onion slices on sheet of foil and brush with remaining 2 tablespoons oil; sprinkle with remaining garlic, then salt and pepper.
  • 4 Prepare barbecue (medium-high heat). Grill chicken pieces until cooked through, about 5 minutes per side; transfer to work surface. Grill vegetables until softened slightly and charred, about 7 minutes per side for onion and 5 minutes per side for zucchini. Transfer to work surface.
  • 5 Grill rolls until toasted, about 2 minutes per side. Spread tarragon mayonnaise on roll bottoms; top with 1 chicken piece, 1/4 of grilled vegetables, and 2 tomato slices. Cover with roll tops.