Combine the all-purpose flour and a pinch of salt in a bowl, and set it aside.

In a large mixing bowl, add the unsalted butter and granulated sugar. Beat on high for about 3-4 minutes until light and fluffy.

Incorporate the egg yolks and vanilla extract into the butter mixture, mixing on high for another minute.

Slowly add the flour mixture to the wet ingredients and stir gently until just combined.

Form the dough into a ball, wrap it in plastic wrap, and chill in the refrigerator for about one hour.

Preheat the oven to 350°F (180°C) and prepare a baking tray with parchment paper.

Once chilled, make approximately 36 small balls of dough and place them on the baking tray.

Use your thumb to create an impression in the center of each ball.

Bake for about 12 minutes, or until the edges are lightly golden.

Remove from the oven and fill the centers with lemon curd while still warm.

Allow the cookies to cool completely on a wire rack at room temperature.