Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a bowl, cream together the butter and sugar until light and fluffy.
Add the egg yolk, vanilla extract, and salt, then mix until combined.
Gradually mix in the gluten-free flour until a dough forms.
Roll the dough into small balls and place them on the prepared baking sheet.
Use your thumb or a spoon to create an indentation in each cookie.
Fill each indentation with a small amount of lemon curd.
Bake for 12-14 minutes or until the edges are lightly golden.
Allow cookies to cool before dusting with powdered sugar, if desired.