Start by chopping the apples, celery, and grapes (if using) into bite-sized pieces. For the apples, try to keep the pieces fairly small for a good mix of texture. If you like, you can lightly toast the walnuts in a dry pan over medium heat for 3-4 minutes, stirring occasionally. This adds a deeper flavor to the nuts, but it’s optional!

In a large mixing bowl, combine the mayonnaise, sugar, lemon juice, and salt. Whisk until smooth and creamy. Taste and adjust for sweetness or tartness by adding a bit more sugar or lemon juice, if needed.

Add the chopped apples, celery, walnuts, and grapes to the bowl with the dressing. Use a large spoon or spatula to gently toss everything together, making sure each ingredient is coated with the dressing. Be careful not to overmix, as the apples and grapes can soften if stirred too much.

You can serve the salad immediately for a fresh, crunchy texture, or refrigerate it for about an hour to let the flavors meld. Give it a quick stir before serving, and enjoy!