Jeanne kelley's marinated and grilled flank steak with arugula salad comes from the "Spring" Chapter in her new kitchen garden cookbook. But with its clean flavors and almost effortless preparation, the dish lands squarely in the realm of summer cooking. What really makes this dish stand out is not the arugulathe real winner is kelley's exotic, tangy sumac and lemon mixture, which performs double duty as marinade and salad dressing.