Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy, about 3-4 minutes.
Mix in the vanilla extract and the egg yolk until fully combined.
In a separate bowl, whisk together the flour and salt. Gradually add the dry mixture to the butter mixture, mixing until just combined.
Gently fold in the lemon zest to the dough for an extra burst of flavor.
Using a tablespoon, scoop out the dough and roll it into balls. Place them on the prepared baking sheet, spaced about 2 inches apart.
Using your thumb or the back of a round measuring teaspoon, make an indentation in the center of each cookie.
Spoon a small amount of the lemon curd into each indentation, being careful not to overfill.
Bake in the preheated oven for 12-15 minutes, or until the edges of the cookies are lightly golden.
Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack. Once fully cooled, dust them with powdered sugar.
Notes
Arrange the cookies on a decorative platter, garnished with fresh mint leaves for a pop of color and a refreshing aroma.