Place flour, sugar, baking powder, lemon zest and salt in bowl of processor. Pulse twice to mix ingredients.
Add chilled butter to flour mixture. Pulse 6-8 times, until the butter is the size of coarse crumbs.
Add egg yolk and 1 tablespoon of lemon juice to bowl. Pulse 3-4 times, until crumbs of dough, when pinched, stay together. If needed, add extra lemon juice to reach this stage.
Place the dough crumbs on a large square of wax paper and squeeze them into a ball and then flatten into a disc, using the wax paper as an aid. Fold the wax paper over the disc to cover it completely and refrigerate for 30 minutes.
Place the disc of dough between two sheets of wax paper that are over 12 inches long. Using a rolling pin, roll the dough out to a circle of approximately 12 inches, turning the wax paper “sandwich” as needed to get the circle as even as possible. (Remember, this is rustic—no need for perfection.)
Remove top layer of wax paper and set aside. Roll dough onto rolling pin and then move it onto the parchment paper on the baking sheet. Cover it again with one of the sheets of wax paper and refrigerate for 15 minutes.
Preheat oven to 350 degrees Place a piece of parchment paper on a heavy baking sheet, rimless if possible.
Remove top wax paper from crust. Turn the edges of the dough over 3/4-inch to create a slightly raised rim. Crimp if desired. Bake for 20 minutes, rotating halfway through, until the crust is golden brown.
Cool the crust in the pan on a rack for 5 minutes. Using parchment paper, lift the crust off of the pan and transfer to serving platter. Cool completely.