In a large bowl whisk together the lemon juice and mustard, seasoning with salt and pepper to taste. Drain the red onion and pat dry. Just prior to serving the salad, add the arugula and red onion to the dressing and toss to coat. Taste and adjust seasoning with additional lemon juice, salt and pepper if necessary. Sprinkle the salad with the shaved Parmesan and serve immediately. Yield: 4 servings Recipe by: Cooking Live Show #CL8905 Posted to MC-Recipe Digest V1 #652 by "Angele and Jon Freeman" on Jun 30, 1997