HEAT oven to 400ºF.
FILLING:
MIX water, granulated sugar and cream of tartar in large saucepan. Bring to boil on medium-high heat. Add crackers; simmer on medium-low heat 5 min., stirring occasionally.
LINE 9-inch pie plate with pie crust as directed on package; fill with cracker mixture. Sprrinkle with lemon juice and cinnamon.
TOPPING:
COMBINE remaining ingredients; sprinkle over Filling.
BAKE 15 min. Reduce oven temperature to 350°F; bake 20 min. or until golden brown. Cool.