01 - Preheat oven to 350°F and line a baking sheet with parchment paper.
02 - In a large bowl, cream butter and sugar until light and fluffy using an electric mixer.
03 - Beat in egg yolk and vanilla extract until fully incorporated.
04 - Gradually mix in flour and salt until just combined, being careful not to overmix.
05 - Roll dough into 1-inch balls and place on prepared baking sheet, spacing 2 inches apart.
06 - Using your thumb or the back of a spoon, gently press an indentation into the center of each ball.
07 - Fill each indentation with about 1/2 teaspoon of lemon curd.
08 - Bake for 10 to 12 minutes, or until edges are just beginning to turn golden.
09 - Cool on baking sheet for 5 minutes before transferring to a wire rack to cool completely. Optionally dust with powdered sugar before serving.