Combine sugar and flour in a medium mixing bowl; add eggs, syrup, 1 tablespoon lemon rind, juice, and butter, mixing well.
Pour filling into pastry shell. Bake at 375° for 10 minutes. Reduce temperature to 350°; bake 45 minutes. Cool to room temperature. Garnish with whipped cream and sprinkle with lemon rind before serving, if desired.