Preheat to 325°F (165°C). Line a baking sheet with parchment paper.

In a large bowl, beat the softened butter on medium-high speed for 2–3 minutes until pale and fluffy.

Add powdered sugar, vanilla extract, lemon zest, and salt. Beat again until light and creamy.

In a separate bowl, whisk together flour and cornstarch. Gradually add to the butter mixture, mixing on low speed just until combined. Do not overmix.

Scoop tablespoon-sized portions and roll into balls or pipe using a star tip for a classic whipped look. Place cookies 2 inches apart.

Chill the shaped cookies for 15–20 minutes for cleaner edges.

Sprinkle with sanding sugar or extra lemon zest if desired.

Bake for 12–15 minutes, until the bottoms are just lightly golden. Tops should remain pale.

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