Preheat your oven to 425°F (220°C). Ensure the oven reaches full temperature before baking for consistent results.

In a medium-sized saucepan, combine 2 cups water, 1 cup white sugar, and 2 teaspoons cream of tartar. Bring the mixture to a boil over medium-high heat, stirring occasionally. Once boiling, carefully add 30 whole buttery round crackers. Continue to boil for 5 minutes, stirring gently to prevent the crackers from sticking together. Remove the saucepan from heat once the crackers have softened.

Pour the cracker mixture evenly into the prepared 9-inch pie shell. Sprinkle ½ teaspoon ground cinnamon evenly over the surface, then drizzle with 1 tablespoon lemon juice to enhance the flavor.

In a separate bowl, combine 1 cup crushed buttery round crackers, ½ cup packed brown sugar, and ½ teaspoon ground cinnamon. Stir the mixture until well blended. Pour in ⅓ cup melted butter, and mix thoroughly until the topping reaches a crumbly consistency resembling coarse sand.

Evenly distribute the prepared crumb topping over the filling. Place the pie in the preheated oven and bake at 425°F (220°C) for 15 minutes. After this initial bake, reduce the oven temperature to 375°F (190°C) and continue baking for an additional 15 to 20 minutes, or until the topping is golden brown and the filling is bubbling slightly at the edges.

Remove the pie from the oven and allow it to cool for 10 to 15 minutes before serving. This dessert is best enjoyed warm, optionally paired with whipped cream or vanilla ice cream.