To make the shrimp cakes, place the shrimp and lemon in a pot with enough water to cover. Bring to a boil, remove from the heat, cover, and let stand 1 minute. Drain, discard the lemon, and when the shrimp are cool enough to handle, peel, devein, and chop them finely.
In a large bowl, combine the shrimp, scallions, celery, bell pepper, parsley, mayonnaise, melted butter, egg, Worcestershire, salt and pepper, and 1 cup of the cornbread crumbs and stir till well blended. Form the mixture into 6 round or oval cakes and coat with the remaining crumbs. Place on a platter, cover with plastic wrap, and chill 1 hour.
Meanwhile, to make the tartar sauce, combine all the ingredients in a bowl, mix till well blended, and set aside.
In a large, heavy skillet, heat the butter and oil over moderate heat till a few crumbs tossed in sputter, add the shrimp cakes, and cook 3 minutes on each side till golden. Drain on paper towels and serve hot with dollops of sauce on top of each.
© 2007 All rights reserved. Published by Houghton Mifflin Harcourt.