Step 1: Preheat your oven to 400°F (200°C). Place your unbaked pie crust into a 9-inch pie plate. Set aside.
Step 2: Coarsely crush the Ritz crackers. You can do this by placing them in a Ziploc bag and crushing them with a rolling pin, or by hand. You want a mix of fine crumbs and small pieces, not uniform powder. Distribute the crushed crackers evenly over the bottom of the unbaked pie crust.
Step 3: In a medium saucepan, combine the 1 1/2 cups granulated sugar, cream of tartar, 1/2 teaspoon cinnamon, and 1/4 teaspoon nutmeg. Whisk to combine.
Step 4: Add the 2 cups of water, lemon juice, and lemon zest to the dry ingredients in the saucepan. Stir well.
Step 5: Bring the mixture to a boil over medium-high heat, stirring constantly, until the sugar is dissolved and the syrup slightly thickens, about 3-5 minutes. It should be clear and syrupy.
Step 6: Carefully pour the hot syrup evenly over the crushed Ritz crackers in the pie crust. The crackers will begin to absorb the liquid.
Step 7: Dot the top of the pie filling with the small pieces of unsalted butter.
Step 8: In a small bowl, mix together the remaining 1 tablespoon granulated sugar and 1/2 teaspoon cinnamon. Sprinkle this mixture evenly over the top of the pie.
Step 9: Bake for 15 minutes at 400°F (200°C). Then, reduce the oven temperature to 350°F (175°C) and continue baking for another 25-30 minutes, or until the crust is golden brown and the filling is bubbly and set.
Step 10: Once baked, remove the pie from the oven and let it cool completely on a wire rack before slicing and serving. This allows the filling to fully set and achieve the correct apple-like texture. Enjoy your Old-Fashioned Mock Apple Pie with Ritz Crackers!