- MIX sugar and cream of tartar in medium saucepan. Gradually stir in water. Bring to boil on high heat; simmer on low 15 minutes Stir in zest and juice; cool 30 minutes.
- HEAT oven to 425°F. Roll out half of pastry on lightly floured surface to 11-inch circle; place in 9-inch pie plate. Place cracker crumbs in crust. Pour sugar syrup over crumbs; top with butter and cinnamon.
- ROLL out remaining pastry to 10-inch circle; place over pie. Seal and flute edge. Cut several slits in top crust to permit steam to escape. Place on parchment-covered baking sheet.
- BAKE 30 to 35 minutes or until golden brown. Cool.
- Note: To prevent crust from overbrowning, cover edge with foil near end of baking time, if necessary.