A flavorful tarragon-dijon marinade makes standard grilled chicken something special. Serve these with a platter of grilled potatoes for a super keep-the-kitchen-cool meal.
In a medium-size glass dish, combine tarragon, mustard, vinegar, water, oil, honey, salt and pepper; add chicken and toss to coat. Cover dish and refrigerate for 1 hour or up to overnight.
Remove chicken from marinade; discard marinade. Evenly divide chicken and onion among 4 long metal skewers.
Off heat, coat a grill rack or grill pan with cooking spray; heat grill to high heat. Cook chicken until no longer pink in middle, turning occasionally for even browning, about 12 minutes (chicken should reach an internal temperature of at least 165°F). Yields 1 skewer per serving.