From the Washington Post.
Ingredients
4 live lobsters (1 1/4 to 1 1/2 pounds each)
1/2 cup (1 stick) unsalted butter, melted
Lemon, for serving (optional)
Instructions
1. In a large, tall stock pot with a tightfitting lid, add about 1 to 2 inches of water. Add a rack or steamer basket to the pot, if using. Bring the water to a boil over high heat. Add two lobsters, more if the pot is large enough, then cover the pot and return the water to a boil. Decrease the heat to medium or medium-low to maintain a vigorous simmer and steam the lobsters until they turn bright red, 13 to 15 minutes.
2. To check to see if the lobster is done, pull on one of the long antennae. If it comes off easily, the lobsters are ready. If not, cook for a few more minutes. (The flesh of cooked lobster should be white with red markings, and the tomalley, or liver, should be green.) Use tongs to remove the lobsters. Check the water level and then repeat this process with the remaining lobsters.
3. Allow lobsters to rest until cool enough to handle, about 5 minutes. Serve warm with melted butter and, if desired, lemon.