A Nantucket Cranberry Pie isn't one of the unique items Trader Joe's dreamed up. It's a real New England specialty, and it brings a bracingly tart flavor you don't often get in overly sweet holiday pies. It's not even what you might normally think of as a pie, being almost a hybrid between pastry and cake. It features a mixture of cranberries and walnuts, cooked in a cake-like batter.