Preheat oven to 400 F. Lightly grease a cookie sheet.
Combine flour, sugar, baking powder, baking soda and salt in medium
bowl. Cut butter in until mixture resembles coarse crumbs. Add sour
cream, apples and vanilla; stirring just until moistened. Turn out dough
onto a floured surface. Knead 4 to five times (dough will be sticky).
Divide dough in half. Gently pat each portion into a circle on a
greased baking sheet. Cut each into four wedges; separate slightly.
Bake for 10-12 minutes, or until slightly browned. When mostly cooled, brush with a powdered sugar glaze (optional).