Ingredients

• 1 10-ounce russet potato, pierced several times with fork
• 1/2 cup nonfat mayonnaise dressing
• 4 teaspoons Dijon mustard
• 1 teaspoon white wine vinegar
• 1/2 teaspoon salt
• 1/4 teaspoon pepper
• 1/2 cup finely chopped fresh basil
• 1/4 cup diced pitted brine-cured black olives (such as Kalamata)
• 4 teaspoons chopped drained capers
• 4 teaspoons minced shallots
• 1 pound skinless boneless fresh tuna steaks, finely chopped
• Nonstick vegetable oil spray
• 4 3-inch-long pieces French bread
• 4 tomato slices
• 4 butter lettuce leaves

Instructions

1. Cook potato in microwave until tender, about 5 minutes per side. Peel potato; mash enough to measure 1/4 cup (packed).
2. Place 1/4 cup mashed potato in bowl. Mix in 1/4 cup mayonnaise, mustard, vinegar, salt and pepper, then 1/4 cup basil, olives, capers and shallots. Add tuna and combine gently. Shape into four 1-inch-thick patties. Mix remaining cup mayonnaise and 1/4 cup basil in small bowl.
3. Prepare barbecue (medium-high heat). Spray both sides of burgers with nonstick spray; grill until just opaque in center, about 4 minutes per side.
4. Cut bread pieces lengthwise into thirds; discard centers. Spread basil mayonnaise on bottom halves. Top with burgers, tomatoes, lettuce and bread tops.