Preparation Mince 1 jar artichoke hearts in processor. Mix in next 5 ingredients. Transfer mixture to large bowl. Add mayonnaise; whisk until smooth. Gradually whisk in oil. Cover; chill dressing for at least 30 minutes to allow flavors to develop. (Can be made 3 days ahead. Cover; keep chilled.) Combine lettuce, onion and tomatoes in bowl. Toss with enough dressing to coat. Divide salad among plates. Top with remaining artichokes and Parmesan.
Preparation Mince 1 jar artichoke hearts in processor. Mix in next 5 ingredients. Transfer mixture to large bowl. Add mayonnaise; whisk until smooth. Gradually whisk in oil. Cover; chill dressing for at least 30 minutes to allow flavors to develop. (Can be made 3 days ahead. Cover; keep chilled.) Combine lettuce, onion and tomatoes in bowl. Toss with enough dressing to coat. Divide salad among plates. Top with remaining artichokes and Parmesan.