Pulse the flour, sugar, salt and lemon zest in a food processor workbowl until combined.
Add the butter and process until the butter forms pea-sized pieces (this will take just a few seconds). Add the ice water and lemon juice and pulse until the dough just begins to come together, but not so much that if forms a ball (that will toughen the dough) Add more water if it looks dry, one teaspoon at a time.
Dump the dough onto a floured counter or work surface. Knead the dough into a smooth ball, then cut into 2 equal pieces. Flatten each piece into a flat disc. Wrap each disc in plastic wrap and refrigerate 1 hour or up to 1 day before using.
Rolling out the dough
Smack one package of dough with a rolling pin to flatten. Unwrap and put the dough on a large floured counter. Sprinkle the top of the dough with more flour and roll the dough firmly away from you, turning the paper after each roll to create a circle about 2 inches larger than your pie dish (12-inches for a 9-inch pie). Sprinkle lightly with more flour if you notice the dough starting to stick.
Pie Crust without a food processor:
In a large bowl, stir together the flour, sugar, salt and zest. Cut the butter into the flour with a pastry blender or a fork until the butter pieces are the size of large peas. Make a well in the center of the flour mix and add the water and lemon juice.
Blend with a fork until the dough starts to come together. If there's flour on the bottom of the bowl, add more water a teaspoon at a time until you can gather the dough into a ball.
If the dough is very firm after chilling, leave at room temperature until it feels pliable.
The key to great, flaky pie crust is starting with cold ingredients - especially the butter and water. One trick is cut the butter and place in the freezer for 15 minutes before mixing the dough. To make ice water, fill a liquid measuring cup with ice cubes, then fill with water. Let sit 5 minutes before measuring and making the dough (don't use the ice, though).
Pie crust dough can be frozen for 3 months. Wrap securely in 2 layers of plastic wrap, then place the package in a zip-tip freezer bag.