First prepare the dressing. Zest the lemon (I like to use a microplane grater) and juice it. Combining all the ingredients in a miniprocessor or blener, or chop the capers by hand and whisk in the other ingredients. Taste and add a pinch of salt if needed.
Peel the kohlrabi very generously with a paring knife to remove any woody parts. Cut the peeled kohlrabi halves and then slice into very thinly (or use a mandoline).
Wash the lettuce leaves and arrange on four salad plates. Spread over the kohlrabi slices. Pour a generous amount of the lemon caper dressing over the sliced kohlrabi. Enjoy.