In a medium saucepan over medium-low heat, whisk together fresh lemon juice, lemon zest, egg yolks, granulated sugar, and salt. Cook the mixture for 20-25 minutes, stirring constantly until it thickens enough to coat the back of a spoon. Once thickened, remove from heat and whisk in cold, cubed butter until fully melted. Transfer to a bowl, cover with plastic wrap directly on the surface, and let it cool completely.

In a spacious bowl, whisk together the all-purpose flour, baking powder, and salt. In a separate large mixing bowl, rub lemon zest into granulated sugar until fragrant. Add softened unsalted butter and cream together until light and fluffy. Next, mix in an egg and vanilla extract, ensuring it's pale and well combined. Gradually incorporate the dry ingredients into the wet mixture, stirring just until combined.

Using a tablespoon, scoop and portion the cookie dough into balls, then roll them into smooth shapes. Make a small indent in the center of each ball for the lemon curd. Chill in the refrigerator for 1 hour.

Preheat your oven to 350°F (175°C). Arrange the chilled cookie dough balls on a prepared baking sheet, leaving space between each. Bake for 8-9 minutes, or until lightly golden. Allow to cool before transferring them to a wire rack.

Once cooled, dust the cookies lightly with powdered sugar. Fill each cookie with about 1 teaspoon of lemon curd for a luscious center.