1Sift oat flour, all-purpose flour, cake flour, and sugar into large bowl. Work butter into flour with fingers or cut in with a pastry blender until flour bits are the size of small peas.
2Using a fork, stir in oil and lemon zest. Slowly add cold water, 1 teaspoon at a time, tossing with fork until moistened without being wet.
3Gather dough with moist hands, shape into flatened round and let rest for 15 minutes. Roll 1/8th inch thick on lightly floured board. (To facilitate rolling dough, you may also roll between 2 pieces of waxed paper.)Or unrolled dough may be placed in pan gently pressed to cover inside of pan.) Gently lift and press onto 8-inch metal pie pan or tart pan (if dough breakes, it is easily patched). Glute edges. Bake at 425 degrees 10 to 12 minutes or until light golden brown.