Lemon Cookie Bars Recipe

Preheat the oven to 350°F. Prepare an 8x8 baking dish by lining it with parchment paper.
In a mixing bowl, combine the dry ingredients by mixing together the flour, sugar, vanilla extract, and salt. Stir in the melted butter until a dough forms.
1 cup all-purpose flour, ¼ cup white sugar, ½ teaspoon vanilla extract, ½ teaspoon salt, ½ cup unsalted butter
Press the dough evenly into the prepared baking dish.
Bake for 18-10 minutes or until golden brown. Remove from the oven and let the crust cool while making the filling.
Make the lemon filling by whisking together sugar, flour, cream of tartar, and salt in a medium bowl. Add eggs, egg yolks, lemon zest, and lemon juice, whisking until smooth.
1 cup white sugar, 2 tablespoons all-purpose flour, 2 teaspoons cream of tartar, ¼ teaspoon salt, 3 large eggs, 3 large egg yolks, 2 teaspoons grated lemon zest, ⅔ cup fresh lemon juice
In a saucepan over medium heat, melt the butter, then slowly whisk in the lemon mixture.
4 tablespoons unsalted butter
Cook, stirring constantly, until the mixture thickens (about 5 minutes).
Pour the filling over the baked crust and spread it into an even layer.
Bake for 6-8 minutes, until the center is set and it slightly jiggles.
Allow the bars to cool completely before slicing.
Dust with colored sugar to top with fresh lemon slices if desired.