Step 1

Put the crab legs in the bottom of a large stockpot, then cover with 4 quarts of water and stir in the seafood seasoning (see Cook's Note). Halve the lemons and squeeze the juice into the pot, then add the rinds. Cover and bring to a boil, then cook over medium-high heat until the crab legs are warmed through, about 5 minutes. Remove the crab legs to a large serving bowl or platter.

Step 2

Meanwhile, melt the butter in a small saucepan over medium-low heat. Cook until the butter foams and simmers, about 1 minute. Remove from the heat and let stand 5 minutes. Using a spoon, remove any milk solids from the surface of the butter, then slowly pour the melted butter into a small serving bowl, leaving any watery, white whey behind in the saucepan. Serve alongside the crab legs.