01 - Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.
02 - In a large bowl, beat softened butter and granulated sugar with electric mixer until light and fluffy, approximately 2-3 minutes.
03 - Mix in egg yolk and vanilla extract until fully incorporated.
04 - Gradually blend in all-purpose flour and salt, mixing just until dough comes together. Do not overmix.
05 - Roll dough into 1-inch balls, approximately 2.5 cm diameter. Place on prepared baking sheet, spacing 2 inches apart.
06 - Using thumb or back of spoon, press gentle indentation into center of each dough ball, being careful not to crack edges.
07 - Spoon approximately 1/2 teaspoon lemon curd into each indentation, filling level with dough edges.
08 - Bake for 10-12 minutes until edges are just beginning to turn golden brown. Centers should remain pale.
09 - Let cookies rest on baking sheet for 5 minutes to set, then transfer to wire rack to cool completely.
10 - Dust cooled cookies generously with powdered sugar before serving, if desired.