01 - Preheat oven to 350°F and line a baking sheet with parchment paper.
02 - In a large bowl, beat butter and sugar until light and fluffy.
03 - Mix in egg yolk and vanilla extract until combined.
04 - Gradually incorporate flour and salt until dough just comes together.
05 - Roll dough into 1-inch balls and place 2 inches apart on prepared baking sheet.
06 - Press center of each ball with thumb or spoon to form a well.
07 - Spoon 1/2 teaspoon lemon curd into each indentation.
08 - Bake for 10-12 minutes until edges begin to turn golden.
09 - Let cookies rest on baking sheet for 5 minutes, then transfer to wire rack to cool completely.
10 - Dust cooled cookies with powdered sugar if desired.