Preheat your oven to 350°F (175°C) and prepare an 8x8-inch baking pan lined with parchment paper.

In a large mixing bowl, whisk together flour, granulated sugar, and salt. Cut in cold unsalted butter until it resembles coarse crumbs, then stir in vanilla extract.

Press two-thirds of the crumb mixture into the bottom of the prepared pan to form the crust.

Par-bake the crust in the preheated oven for about 15 minutes until lightly golden.

In a medium bowl, whisk eggs and granulated sugar until smooth, then mix in flour, lemon zest, lemon juice, and a pinch of salt until thickened.

Pour the lemon filling over the warm crust and sprinkle with the reserved crumb mixture.

Bake for 20 to 23 minutes until the lemon filling is set and the topping is golden brown.

Allow to cool at room temperature for 30 minutes, then chill in the refrigerator for at least 1 hour.

Lift the bars out using the parchment paper, slice into squares, and serve.