Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
Cream butter and powdered sugar in a large bowl until light and fluffy.
Mix in vanilla extract, lemon extract, and lemon zest for a bright citrus flavor.
Gradually sift in flour, cornstarch, and salt. Mix until a soft dough forms. Add a teaspoon of milk if the dough feels dry.
Scoop 1 tbsp of dough and flatten it in your palm. Add ½ tsp of lemon curd in the center. Wrap dough around the curd and roll into a ball.
Place cookies on the baking sheet, 2 inches apart. Bake for 12–14 minutes, until set but not browned.
Cool on the baking sheet for 5 minutes, then transfer to a wire rack. Once cooled, dust with powdered sugar for a bakery-style finish.