1. Wash, clean and cut celery into 1/2 inch cubes, and transfer into a mixing bowl.
2. Using a knife, dice onion very finely and add to the celery.
3. Using a knife, skin, quarter and deseed the apples. Cut into 1/2 inch cubes and put in the other ingredients.
4. Season lightly. Pour in lemon juice and toss well.
5. Serve in a glass bowl as a side accompaniment for cold meats.