Peel apples, remove the core, cut into cubes, mix with half the lemon juice so it doesn't brown.
Peel celeriac and place in boiling water for a minute. Remove celeriac and cut into thin sticks, mix with the rest of the lemon juice and add to apples.
Place raisins in boiling water and set aside for 3 minutes. Drain raisins and add to vegetables. Sprinkle everything with freshly ground black pepper and cinnamon.
Add arugula, mayonnaise, roughly chopped and toasted walnuts. Sprinkle with salt and mix all ingredients.