In a medium bowl, whisk together all-purpose flour, cornstarch, zest of one lemon, and salt until evenly combined.

In a large mixing bowl, beat softened butter and powdered sugar together using a hand mixer on medium speed for 3-5 minutes until light and fluffy.

Slowly add half of the dry mixture to the butter, followed by lemon juice. Mix on low speed until well incorporated. Gradually add the remaining dry ingredients with a spatula, folding gently until a cohesive dough forms.

Transfer the dough onto parchment paper. Roll it into a log about 1.5 inches wide, wrap tightly and refrigerate for 1 hour.

Preheat your oven to 320°F (160°C). Slice the chilled dough into 1/2 inch thick rounds, placed on a parchment-lined baking sheet, spaced about an inch apart.

Increase your oven temperature to 350°F (180°C) and bake cookies for 5 minutes. Then, keep watching as you bake for an additional 9-10 minutes, until edges turn light golden.

Allow cookies to cool on the baking sheet for 5 minutes then transfer to a wire rack to cool completely.

In a small bowl, whisk together powdered sugar and fresh lemon juice until smooth. Drizzle or spread over cooled cookies.