For the lemon curd:

1. In a medium bowl, whisk together the sugar, cornstarch, and salt until no lumps remain.
2. In a medium saucepan over low-medium heat, melt the butter.
3. Whisk in the sugar mixture, then the lemon juice and egg yolks until fully combined, about 1 minute.
4. Use a rubber spatula to constantly stir the mixture for another 2-3 minutes or until large bubbles form in the center. Immediately remove from heat.
5. Strain the lemon curd into a bowl. Press plastic wrap up against the surface to prevent a skin from forming, and chill for at least 2 hours or overnight.

For the cream cheese cookies:

1. In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
2. In the bowl of a stand mixer fitted with a paddle attachment, cream the butter, cream cheese, and sugar together for about 2-3 minutes on medium speed.
3. Add in the egg, egg yolk, and vanilla, and mix until fully combined.
4. Lastly, add in the dry ingredients and mix until just combined.
5. Cover the bowl with plastic wrap and chill in the fridge for 30 minutes.
6. Meanwhile, preheat the oven to 350 degrees F and line two baking sheets with parchment paper.
7. Once the dough has chilled, use a 2 tbsp cookie scoop to portion the dough.
8. Roll each cookie dough ball in your hands, then roll in the powdered sugar and place on the baking sheet spaced about 2 inches apart.
9. Flatten the cookie dough out slightly (as pictured above) and bake for about 12 minutes.
10. Once the cookies come out of the oven, immediately press the centers with the back of a 1 tbsp spoon.
11. Allow the cookies to cool completely on the baking sheet.

For assembly:

1. Once the cookies are cool, sprinkle each of them with powdered sugar.
2. Add a dollop of lemon curd to the centers of each cookie and serve!