recipe for waldorf salad

Ingredients 2 cups chopped apples (such as Granny Smith or Gala) 1 cup chopped celery 1 cup seedless red grapes, halved 1/2 cup chopped walnuts or pecans 1/2 cup mayonnaise or Greek yogurt 1 tablespoon lemon juice Salt and black pepper to taste Fresh lettuce leaves (optional, for serving)