Preheat oven to 450degrees.
In a medium bowl stir the flour and sugar together.
Use a pastry blender or two butter knives to cut the butter cubes into the flour until pieces are about pea-size.
In a small bowl beat the egg yolks and then add the ice water, stir.
Gradually stir the egg yolk mixture into the flour mixture as best you can, with a fork.
Use your fingers to gently knead the dough until it holds a form. Do NOT over-mix.
Cover dough and refrigerate for 1 hour.
On a lightly floured surface use your hands to gently flatten the dough.
Roll the dough from the center to the edges until a 12 inch circle is formed. Be gentle.
Transfer the dough to a tart pan (for Key Lime pie transfer to a pie pan).