Tangy tomato jam and Vidalia onions add flavor to grilled chicken served on a baguette.
Heat a grill or grill pan over high heat. Pound chicken between two sheets of plastic until 1/2 inch thick. Remove plastic. Sprinkle chicken generously with salt and pepper. Lightly oil grill or grill pan; cook chicken until lightly browned and cooked through, turning halfway through cooking time,10 to 15 minutes on a hot grill pan. (Time will vary depending on the grill.) Set aside.
Toss the onion with olive oil, salt, and pepper, and place on grill until lightly charred and soft, 8 to 10 minutes. Set aside.
Slice baguette lengthwise, and spread both sides with tomato jam. Slice chicken into 1/4-inch strips. Layer one side of baguette with chicken, reserved onions, and the arugula. Top with other side of bread, tomato jam facing down. Slice into three six-inch sandwiches.