Cut margarine into 5–6 slices each. With steel blade of food processor in place, add flour, salt and slices of margarine. Process until mixture resembles coarse oatmeal.

Break egg into measuring cup. Add lemon juice and enough cold water to make contents equal 1/2 cup. Beat to blend. With food processor running, add liquid in a steady stream through the feed tube. Stop as soon as pastry gathers into a ball.

Cut and shape into two smooth flat halves,smoothing out any cracks or seams. Turn out onto two pieces of saran wrap, and wrap each half tightly. Chill for 20 minutes. When ready to roll our, well chilled dough, let it sit at room temperature to soften for several minutes. Roll out between two pieces of parchment paper or waxed paper until 1/8 inch thick. Fit into pie pan or whatever else you intend to use it for. Makes enough dough for one 10 inch pie or two 10 inch quiches. Bake at 400°F for 18 minutes, or until lightly browned if you need to bake it before filling