Core and chop 2 large apples into ½-inch cubes, leaving skin on. Immediately toss with 1 tablespoon lemon juice in a large mixing bowl to coat all surfaces and prevent browning.
2 large apple, 1 tablespoon lemon juice
Slice 2 celery stalks into ¼-inch pieces and halve 1 cup grapes for even distribution in the salad.
2 stalks celery, 1 cup grapes
Whisk ½ cup mayonnaise, remaining lemon juice if any, ¼ teaspoon salt, and ⅛ teaspoon black pepper in a small bowl until smooth and creamy with no lumps. Taste and adjust salt if needed.
0.5 cup mayonnaise, 1 tablespoon lemon juice, 0.25 teaspoon salt, 0.125 teaspoon black pepper
Add chopped celery, halved grapes, and ½ cup toasted walnuts to the bowl with apples. Pour dressing over the salad and toss gently until all ingredients are evenly coated.
2 large apple, 2 stalks celery, 1 cup grapes, 0.5 cup walnuts, 0.5 cup mayonnaise
Cover the bowl or transfer to an airtight container. Refrigerate for at least 30 minutes to let flavors blend and maintain crisp textures before serving, optionally on lettuce leaves.
