In a small bowl, mix the buttermilk with the vanilla. Add to the dry ingredients and stir with a fork just until the dough comes together. Turn the dough out onto a lightly floured surface and knead twice. Pat the dough into a round and cut into 8 wedges. With lightly floured hands, pat the wedges into 1/2-inch-thick rounds. Set the rounds on the prepared baking sheet and bake for 12 to 14 minutes, or until the scones are puffed and pale golden. Transfer to a rack and cool before serving.