Method:

• Heat oven to 350°F. Spray bottom and sides of 9-inch glass pie plate with cooking spray (without flour). In medium bowl, mix all flours, 1 tablespoon sugar and 1/2 teaspoon salt; set aside.
• In food processor, place egg, oil, 1/4 cup water, the vinegar, xanthan gum and guar gum. Cover; process 2 minutes. Add flour mixture. Cover; process 1 minute or until well mixed. Place 1 cup of dough in medium bowl. Stir in walnuts and 1/4 cup sugar; set aside. Press remaining dough (about 2 cups) in bottom and up side of pie plate.
• In 3-quart saucepan, place apples, 1/2 cup sugar, 1/4 cup water, 1/8 teaspoon salt, the cinnamon and nutmeg. Heat to boiling over high heat. Reduce heat to medium-low; cook 10 minutes, stirring occasionally.
• In small bowl, mix cornstarch and 2 tablespoons water until smooth. Add to apple mixture; cook and stir about 1 minute or until thickened. Pour filling into crust. Crumble walnut dough evenly over filling.
• Bake 55 to 60 minutes or until crust is medium brown and filling is bubbly. Cool at least 1 hour before serving.