Finely slice the kohlrabi using a mandolin, so it’s about 1mm thick. Do the same with the apple, leaving the skin on and taking care to avoid the core. Put them into a mixing bowl, add the yogurt, most of the dill and ½ the lemon zest, and season with salt and pepper. Mix well until all the slices are coated.
Arrange on a plate, finishing with a good twist of black pepper on top. Add the rest of the lemon zest and remaining dill and drizzle a little olive oil over.