waldorf salad recipe

6 tablespoons mayonnaise (or plain yogurt) 1 tablespoon lemon juice 1/2 teaspoon kosher salt Pinch freshly ground black pepper 2 sweet apples, cored and chopped 1 cup seedless red grapes, halved, or 1/4 cup raisins 1 cup thinly sliced celery 1 cup chopped, slightly toasted walnuts