Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a large bowl, use an electric mixer to cream the softened butter and ½ cup of powdered sugar until light and fluffy, approximately 2-3 minutes.
Add the cornstarch, all-purpose flour, lemon zest, lemon juice, vanilla extract, and salt. Mix on low speed until just combined and a soft dough forms.
Shape the dough into 1-inch balls and arrange them about 2 inches apart on the prepared baking sheet. Gently flatten each ball with the tines of a fork.
Bake for 10-12 minutes, or until the edges are a very light golden brown.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
Once the cookies are completely cool, dust them generously with additional powdered sugar.
