Preheat oven to 375 degrees F. Coat a baking sheet with cooking spray. In a large bowl, combine 1-1/2 cups flour,baking soda,salt,2 tablespoons sugar, and cream of tartar. Cut in butter with a pastry blender or 2 forks until mixture resembles coarse meal. Stir in cranberries and orange rind, tossing well. Add buttermilk, stirring just until dry ingredients are moistened.
Sprinkle remaining flour evenly over work surface. Turn dough out onto floured surface; knead 4 or 5 times. Divide dough into 2 portions. Pat each portion into a 5-inch circle on prepared baking sheet . Cut each circle into 4 wedges, cutting to, but not through, bottom of dough. Sprinkle each circle evenly with remaining sugar. Bake 20 minutes, or until golden.