2 large Granny Smith apples, peeled and cut into thin matchsticks
Two 6-ounce bunches watercress, thick stems discarded
In a large bowl, whisk the cider vinegar with the sugar and buttermilk. Gradually whisk in the vegetable oil and season the cider dressing with salt and freshly ground black pepper. Add the apple matchsticks and watercress and toss to coat the salad. Serve the apple salad right away.