Preheat the oven to 425 degrees F.

Fill a large stockpot 3/4 full with salted water and bring to a boil. Plunge the lobster headfirst into the boiling water and cook, covered, until firm and almost cooked through, about 7 minutes. Drain and transfer with tongs to a large bowl filled with ice water. Drain well. When the lobster is cool enough to handle, place it on a cutting board, back side down flat on its back. With a sharp knife, cut down through the middle of the lobster from head to tail, forming 2 identical halves. Lift out the pink coral and any green tomalley. Reserve for another use or discard. Remove the stomach sac from the back of the head, the black vein running from head to tail, and any spongy gray tissue. Discard. Place the 2 lobster halves on a baking sheet and set aside while you prepare the stuffing.

In a mixing bowl combine the crushed crackers, crabmeat, 1/3 cup of the butter, the parsley, tarragon, thyme, lemon zest and juice and toss to combine. Adjust seasonings with salt and white pepper.

Divide the stuffing evenly among the 2 lobster halves, filling the empty cavity and covering the tail with the remaining stuffing. Drizzle the 2 halves with the remaining butter, and bake the lobsters until the filling is golden brown on top and the lobsters are heated through and thoroughly cooked, about 10 to 12 minutes. (The temperature on an instant-read thermometer inserted into the lobster meat should register 145 degrees F.)