1. Combine 6 cups water and 1 tablespoon juice in a large bowl. Working with 1 artichoke at a time, cut off stem of artichoke to within 1 inch of base; peel stem. Remove bottom leaves and tough outer leaves from artichoke, leaving tender heart and bottom. Trim about 1 inch from top of artichoke. Place artichoke in lemon water. Repeat procedure with remaining artichokes. Drain and set aside.
2. Place onion in center of a Dutch oven. Arrange artichokes in a single layer around onion. Add broth and remaining ingredients to pan; bring to a boil. Cover, reduce heat, and simmer 18 minutes or just until onion is tender (artichokes will be very tender). Stir in remaining 1 tablespoon juice. Remove artichokes and onion from pan with a slotted spoon; set aside, and keep warm. Bring broth mixture to a boil; cook 4 minutes or until slightly thickened. Pour sauce over artichoke mixture.