**Prepare the Crust:**

Preheat your oven to 350°F (175°C). In a mixing bowl, combine the flour and powdered sugar. Cut in the cold butter using a pastry cutter or fork until the mixture resembles coarse crumbs. If needed, add cold water, 1 teaspoon at a time, until the dough comes together.

**Bake the Crusts:**

Press a small amount of dough into each cup of a mini muffin tin, forming a thin, even layer on the bottom and sides. Bake for 10-12 minutes, or until lightly golden. Let cool completely.

**Make the Lemon Filling:**

In a saucepan over medium heat, whisk together the egg yolks, granulated sugar, lemon juice, and lemon zest. Cook while stirring until the mixture thickens, about 5 minutes. Remove from heat and stir in the butter until smooth. Cool slightly, then spoon the lemon filling into the cooled crusts.

**Prepare the Meringue:**

In a clean mixing bowl, beat the egg whites and cream of tartar until soft peaks form. Gradually add the granulated sugar, 1 tablespoon at a time, beating until stiff, glossy peaks form.

**Top with Meringue:**

Use a piping bag or spoon to dollop or swirl meringue onto each lemon-filled cup.

**Bake and Finish:**

Return the filled cups to the oven and bake for 5-7 minutes, or until the meringue is lightly golden. Cool completely on a rack before serving.