Makes enough for one tart.
For the ice water, fill a cup with water, add in an ice cube and put it in the freezer while you measure out the rest of your ingredients. You will only be using some of this ice water.
Cut up the butter into 1/2 inch cubes. Add the cubed butter to the flour mixture and pulse the processor until the butter is about the size of peas. Check after 10 or 12 pulses, then pulse a few more times, if needed.
Pour the flour mixture into a medium size bowl. Add about 4 tablespoons of ice water and gently mix with your fingers. Keep adding in more water, a tablespoon or even a teaspoon at a time until clumps of dough start to form and you no longer see dry bits of flour. The dough should be moist and come together when pressed but not wet and sticky. See notes.
Dump the dough on to a floured counter top and gather into a ball. Take the ball of tart dough and place it on to a piece of plastic wrap. Bring the wrap up around the sides of the dough and over the top to cover the dough. Press down on the ball of dough to make a disc. Round out the sides so it looks like a neat disc of dough. You should see flecks of cold butter in the dough. Refrigerate for at least 30 minutes.
Take out the cold dough and place it on a floured counter top. Roll out the dough with a rolling pin, starting back about 2/3 from the edge, then turn the dough a bit and roll again. Keep rolling and turning the dough until you have formed the shape of a circle approximately 14" in diameter and about 1/4" thick. Only roll the dough in one direction, never back and forth. Add more flour if the dough starts to stick to the counter.
Loosely roll up the pastry dough onto the rolling pin and then gently unroll it on to the tart pan. Press the dough into the bottom of the tart pan and neatly up the sides. Fold more dough into the sides if it appears too thin in some spots. Trim off any excess dough with a knife or roll over the top with the rolling pin to cut off the extra pieces. Cover and refrigerate for 30 minutes or until you are ready to precede with your recipe.