Preheat the oven to 425 degrees F (220 degrees C).
Bring water, sugar, and cream of tartar to a boil in a medium saucepan over medium-high heat.
Drop in whole crackers and boil for 5 minutes.
Remove from the heat and pour mixture into pie shell; sprinkle with cinnamon and drizzle with lemon juice.
Mix crushed crackers, brown sugar, melted butter, and cinnamon together in a small bowl; sprinkle over pie filling.
Bake in the preheated oven for 15 minutes.
Reduce the heat to 375 degrees F (190 degrees C) and continue to bake for 15 to 20 more minutes.
Serve warm.
