Mix the mayonnaise, balsamic and lemon juice in a bowl, season.
Dry roast the nuts in a frying pan until golden brown, remove and set aside. Heat the oil in the same pan. Sauté the Swiss chard for approx. 5 mins., season with salt, allow to cool slightly.
Mix the Swiss chard, celery, grapes and apple with the dressing. Sprinkle the nuts on top.