Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.
In a large mixing bowl, beat the softened butter with granulated sugar and powdered sugar until light and fluffy, about 3-4 minutes.
Mix in the vanilla extract until fully incorporated.
In a separate bowl, whisk together the all-purpose flour, salt, and baking powder.
Gradually add the dry mixture to the butter mixture. Mix until you have a crumbly, cohesive dough.
Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheets, leaving space between each cookie.
Using your thumb or the back of a rounded measuring spoon, gently press down in the center of each dough ball to create an indentation for the lemon curd.
Spoon a small amount of lemon curd into each thumbprint, filling it generously without overflowing.
Place the baking sheets in the preheated oven and bake for 12-15 minutes, or until the edges are lightly golden.
Once out of the oven, let the cookies cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.
Optional - Dust the cooled cookies with powdered sugar for a sweet finish and an elegant appearance.
Notes
Optional - Dust with powdered sugar for an elegant finish.