In a medium bowl, combine smoked duck with next 8 ingredients and toss. In another bowl, whisk together vinegar and next 5 ingredients. While whisking, add oil in a thin stream until emulsified. Add dressing to salad mixture, reserving a few teaspoons to drizzle over lettuce. Toss to coat salad mixture. Mound lettuce on plates. Mound salad over lettuce. Garnish with tomato and drizzle reserved dressing over lettuce and tomato.