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

Methods:

Cook potato in microwave until tender,about 5 minutes per side.Peel potato;mash enough to measure 1/4 cup (packed).

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.

Prepare barbecue (medium-high heat). Spray both sides of burgers with nonstick spray; grill until just opaque in center,about 4 minutes per side.

Cut bread pieces lengthwise into thirds; discard centers.Spread basil mayonnaise on bottom halves.Top with burgers,tomatoes,lettuce and bread tops.