In a medium saucepan, whisk together eggs, lemon juice, lemon zest, and granulated sugar over low heat.

Add the unsalted butter and continue whisking for about 5 minutes.

Gradually increase the heat, stirring constantly until thickened for about 5-10 minutes, reaching a temperature of 170-175°F.

Strain the curd through a fine mesh sieve into a bowl, then cool to room temperature.

Preheat your oven to 350°F and line baking sheets with parchment paper.

In a mixing bowl, combine all-purpose flour and a pinch of salt; set aside.

In another bowl, cream the softened butter and granulated sugar until light and fluffy, about 3-4 minutes.

Blend in the egg yolk and vanilla extract, then gradually incorporate the dry ingredients until a cohesive dough forms.

Scoop the cookie dough into 1-tablespoon-sized balls, rolling them between your palms until smooth.

Roll each ball in powdered sugar for an extra touch of sweetness, then use your thumb to make a deep indentation in the center of each ball.

Carefully spoon the cooled lemon curd into the indentations you created on each cookie dough ball.

Transfer the filled cookie dough balls onto the lined baking sheets, spacing them about 2 inches apart.

Bake in your preheated oven for 12-14 minutes, or until the edges are just lightly golden.

Once baked, remove the Lemon Curd Cookies from the oven and let them cool on the baking sheets for about 5 minutes.

Then, gently transfer them to a wire rack to cool completely.

Dust with additional powdered sugar before serving if desired.