In a stand mixer, cream butter with granulated sugar and powdered sugar on medium-low speed for about 1 minute until smooth and fluffy. Add orange zest.

Add egg and vanilla extract into the mixture and continue mixing until well incorporated.

Gradually add salt, cornstarch, all-purpose flour, and cake flour, mixing on low speed until dough comes together.

Shape the dough into a log, wrap tightly in plastic wrap, and refrigerate for at least 2 hours.

Preheat oven to 350°F (175°C) and prepare a baking sheet with parchment paper.

Remove dough, cut log into 1/4 inch thick slices, and bake for 10-13 minutes or until edges are lightly golden.

Allow cookies to cool on the baking sheet for about 5 minutes before transferring to a wire rack.