In a large bowl, whisk together the all-purpose flour, powdered sugar, and salt. Cut in the chilled butter until the mixture resembles coarse crumbs. Gather the dough into a ball, wrap it in plastic wrap, and refrigerate for at least 30 minutes.

Preheat your oven to 350°F (175°C). Roll out the chilled dough to about 1/8-inch thick. Cut out circles with a cookie cutter and place them on a baking sheet. Bake for 8-10 minutes until lightly golden. Let them cool completely.

In a saucepan over medium heat, whisk together lemon juice, granulated sugar, egg yolk, cornstarch, and lemon zest. Cook until thickened and bubbly, then remove from heat and let cool completely.

Beat egg whites in a clean mixing bowl until foamy. Add cream of tartar and continue beating until soft peaks form. Gradually add granulated sugar until stiff peaks form.

Spoon lemon filling onto each cooled cookie and top with meringue. Broil for 1-2 minutes until golden brown. Let cool completely before serving.

Store leftovers in an airtight container in the fridge for up to three days. Reheat gently in an oven at low temperature.