Fill a large steamer or soup pot, with about 2 inches of water, add the salt and squeeze in the lemon juice; toss the halves in there too for extra flavor. Bring to a boil over medium heat.
Place the lobsters in the steamer basket or directly in the pot, cover, and allow to steam until they turn bright red, about 15 minutes. Remove the lobsters from the pot and cool to room temperature, and then chill thoroughly before cracking open. Serve with lemon wedges and Lemon-Caper Mayonnaise as part of a raw shellfish bar.
Combine all ingredients in a mixing bowl and blend with a wooden spoon to combine. Set aside to allow the flavors to marry. Serve as a dipping sauce with steamed lobster and poached shrimp.