This simple salad recreates a dish we had in Shaffa Bar, Shira Petel’s restaurant in Tel Aviv. It’s a perfect fusion of sweet, sharp and peppery flavors. We prefer black grapes because they take on a lovely hue when roasted (broiled, really) and lend that color to the thinly sliced onion during their brief marination in vinegar. Look for mature arugula sold in bunches instead of packaged baby arugula; bunched arugula requires a little more prep but its more assertive flavor is a better match for the sweetness of the grapes.