Fill a large stockpot about half full of water. Add the salt and bring to a boil. When the water has come to a rolling boil, plunge the lobsters headfirst into the pot. Clamp the lid back on tightly and return the water to a boil over high heat. Reduce the heat to medium and cook the lobsters for 12 to 18 minutes (hard-shell lobsters will take the longer time), until the shells turn bright red and the tail meat is firm and opaque when checked.
Lift the lobsters out of the water with tongs and drain in a colander. Place underside up on a work surface and, grasping firmly, split the tails lengthwise with a large knife. Drain off the excess liquid. Serve with melted butter and lemon wedges.
Lobsters must be kept alive until they are cooked because their flesh begins to deteriorate soon after they die or are killed. Some experts recommend numbing the lobsters first by placing them in the freezer for about 10 minutes before cooking.
Recipe courtesy of Brooke Dojny, "The New England Clam Shack Cookbook", Storey Books, 2003