Heat oven to 350°. Positions rack in lower third of oven. Stir together sugar and flour in a bowl. Add to eggs in another bowl and beat until light in color and slightly thickened, about 3 minutes. Stir in lemon rind, lemon juice, butter, vanilla and almond extract. Pour into pie shell. Place pie on baking sheet. Bake in lower third of oven for 20-25 minutes or until filling is set and lightly browned. Meanwhile, toast the slivered almonds in a skillet over medium-high heat, stirring, until just lightly browned, about 4-5 minutes. Sprinkle toasted almonds over top of the pie. Cool pie on a wire rack.