In a medium saucepan, whisk together lemon juice, lemon zest, egg yolks, sugar, and salt. Cook over medium-low heat, stirring constantly for about 20–25 minutes until thickened. Remove from heat and stir in cold butter until smooth. Cool completely in fridge.

In a bowl, whisk together flour, baking powder, and salt. In another bowl, cream softened butter and sugar for 2–3 minutes until light. Mix in egg yolk, vanilla, and lemon zest. Fold in dry ingredients and chill dough for 1 hour.

Preheat oven to 350°F. Scoop tablespoon-sized balls of dough onto a lined sheet, spacing 2 inches apart. Make a shallow indentation in each ball. Bake for 9–10 minutes until edges are golden.

Fill each indentation with lemon curd after baking. Optionally dust with powdered sugar before serving.