A buttery shortbread crust that is sturdy but tender enough to bite through and a thick, luscious filling with a balance of sweetness and tangy lemon brightness.
Add flour, sugar, powdered sugar, lemon zest, and salt in a food processor. Pulse to combine.
Add butter and pulse until mixture resembles coarse crumbs.
Pour crust mixture into a parchment lined baking dish and press to create an even layer.
Bake crust for 20-25 minutes at 325°F until golden brown.
Place the whole eggs, egg yolk, granulated sugar, powdered sugar, zest, and salt in a large bowl and whisk to combine.
Whisk in the lemon juice, and then the flour, until combined.
Pour lemon filling mixture over crust and bake until light brown around the edges, about 15-20 minutes.
Cool on wire rack for an hour before dusting with powdered sugar and serving.