For the vegetable-apple salad, first squeeze the lemon. Peel the apples and celeriac, grate finely and sprinkle with the lemon juice.
Peel the carrot and grate finely as well. Put celery, apples and carrots in a bowl. Add sugar, salt, pepper, the natural yogurt and add the chopped walnuts.
Everything should then be left at room temperature for an hour.