1 tablespoon kosher salt, plus more as needed
2 (1-1/2-pound) whole live lobsters
3 whole black peppercorns
1/4 bay leaf
1 cup water, plus more for steaming the lobsters
6 tablespoons unsalted butter (3/4 stick), cut into 1/2-inch cubes and chilled
1 tablespoon finely chopped tarragon leaves
1 1/2 teaspoons freshly squeezed lemon juice
Freshly ground black pepper
2 tablespoons unsalted butter (1/4 stick), softened
4 top-split hot dog buns