Preheat the oven to 350 degrees F.
In a small bowl, combine the flour and sugar, and lemon zest.
Cut the butter into small cubes, then, using a pastry cutter or your fingers, crumble the butter into the flour mixture until even crumbs form.
Stir in the egg yolk and vanilla.
Using a spoon or your hands, bring the dough together until it forms a ball.
Take 1/3 of the dough ball and pat it out evenly onto the bottom of the springform pan (keep the sides off the pan for now). If needed, use slightly more than 1/3, but it should be enough to form a thin, even layer across the pan.
Place the bottom crust into the oven and bake for 7 minutes.
Remove the bottom crust and set it on a rack to cool. Reduce the heat to 250 degrees F.
When the bottom crust has cooled, attach the sides to the springform pan.
Pat the remaining dough onto the sides of the pan to a height of about 1 1/4 inches. It should meet the cooled bottom crust and press evenly up the sides all around. (see tips and photos above for how to do this neatly.)
Set aside while you prepare the filling.