1. Prepare a charcoal or gas grill for direct cooking over medium-high heat. Coat grate with cooking spray.
2. Grate apple to the core. Wrap shredded apple in a clean kitchen towel and squeeze to remove excess juice.
3. In a large bowl, stir together apple, chicken, shallot, mustard, salt, and pepper until well combined.
4. Shape into six 3/4-inch-thick patties about 6 oz. each and refrigerate, covered,  30 minutes.
5. Prepare Cherry Tomato Aioli.
6. Grill patties 12 to 14 minutes or until cooked through and no longer pink (165°F), turning once halfway through.
7. During the last 2 minutes of grilling, place buns cut sides down to toast.
8. Remove food from grill and let patties rest for 5 minutes.
9. To serve chicken burgers, spread Cherry Tomato Aioli on bun bottoms and layer with patties, arugula, tomato slices, and onion.
10. Add bun tops.

Cherry Tomato Aioli:

1. In a blender, combine 1 cup mayonnaise, 1/4 cup cherry tomatoes, 1 Tbsp. tomato paste, 1 Tbsp. fresh lemon juice, 2 tsp. minced garlic until smooth. Season to taste.

Each burger contains:  626 calories, 42 g fat,  8 g saturated fat, 0 g trans fat, 146 mg cholesterol,  698 mg sodium, 31 g carbohydrates, 3 g fiber, 9 g sugar, 32 g protein. Daily values: 10% vitamin A, 11% vitamin C, 7% calcium, 18% iron.