Lightly coat a 9x9-inch baking pan with cooking spray; set aside. For pastry: In medium bowl, stir together unbleached flour, oat flour and salt. Using pastry blender, cut in the 1/4 cup butter or margarine until pieces are pea-size. Sprinkle 1 tablespoon of the cold water over part of the flour mixture; gently toss with a fork to mix. Push moistened pastry to side of bowl. Repeat moistening flour mixture, using 1 tablespoon of water at a time, until all of the flour mixture is moistened. Form dough into a ball.
On lightly floured surface, use your hands to slightly flatten pastry into a square. Roll pastry from center to edges into 9x9-inch square, lightly dusting with flour as needed. Set aside.
In a large bowl, combine eggs, sugar, corn syrup, the 3 tablespoons melted butter or margarine and vanilla. Pour one-third of egg mixture into prepared pan. Stir pecans into remaining egg mixture.
Wrap pastry around the rolling pin. Unroll on top of egg mixture in baking dish. Slowly pour nut mixture over pastry.
Bake in a 350 degree F oven for 45 to 50 minutes or until a knife inserted near the center comes out clean. Cool 45 minutes before serving. Serve with vanilla ice cream.
Cover and chill within 2 hours. Makes 12 servings.
If you can't find oat flour at your supermarket, place 2/3 cup rolled oats in a blender or food processor. Cover and blend or process until finely ground. Measure 1/2 cup.