Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.

Cream the softened butter and powdered sugar together until light and fluffy (about 2-3 minutes).

Beat in the lemon zest, lemon juice, and vanilla extract until just combined.

In a separate bowl, whisk together the flour, cornstarch, and salt.

Gradually add the dry ingredients to the butter mixture, mixing on low speed just until a soft dough forms. Do not overmix.

Roll the dough into 1-inch balls and place 2 inches apart on the baking sheets.

Use your thumb or the back of a small spoon to gently press an indentation into the center of each dough ball.

Chill the baking sheets with the cookies in the refrigerator for at least 30 minutes.

Bake for 12-14 minutes until edges are barely golden. Let cool on the pan for 5 minutes.

Spoon a small amount of lemon curd into the indentation of each warm cookie.

Once cookies are mostly cool, generously dust the tops with extra powdered sugar. Let cool completely before storing.