1. Preheat oven to 400°.
2. Combine first 5 ingredients in a bowl; cut in margarine with a pastry blender until mixture resembles coarse meal. Add cherries, and toss well. Combine egg and buttermilk; add to dry ingredients, stirring just until moistened (dough will be sticky).
3. Turn dough out onto a lightly floured surface; with floured hands, knead 4 or 5 times. Pat dough into an 8-inch circle on a baking sheet coated with cooking spray. Cut into 12 wedges, cutting to but not through bottom of dough. Brush with egg white, and sprinkle with 1 tablespoon sugar. Bake at 400° for 15 minutes or until golden. Serve hot.