Preheat your oven to 350°F (175°C). Prepare an 8x8-inch baking pan by lining it with parchment paper, leaving some overhang.

In a mixing bowl, combine the flour, granulated sugar, and salt. Incorporate the cold, cubed butter until the mixture resembles coarse crumbs.

Stir in the vanilla extract, then firmly press two-thirds of this mixture into the base of your prepared pan to form the crust. Set aside the remaining third for topping.

Bake the crust for 15 minutes or until it turns a light golden brown. Let it cool slightly.

In another bowl, whisk together the eggs and granulated sugar until smooth. Add the flour, lemon zest, lemon juice, and a pinch of salt, whisking until fully combined and slightly thickened.

Pour the lemon mixture over your warm crust and evenly sprinkle the reserved crumble mixture on top.

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

Allow to cool in the pan for about 30 minutes before transferring to the fridge for at least 1 hour.

Lift the bars out using the parchment overhang and cut into squares.