01 - Preheat oven to 350°F and line baking sheet with parchment paper.
02 - Cream softened butter and granulated sugar in large bowl until light and fluffy.
03 - Beat in egg yolk and vanilla extract until well incorporated.
04 - Gradually mix in 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 thumb or back of spoon into center of each ball to create deep well.
07 - Fill each indentation with approximately 1/2 teaspoon lemon curd.
08 - Bake for 10-12 minutes until edges just begin turning golden brown.
09 - Let cool on baking sheet for 5 minutes, then transfer to wire rack to cool completely.
10 - Dust cooled cookies with powdered sugar if desired before serving.