Thinly slice the zucchini and onion on a mandolin – break the onion into rings.
Mix all ingredients for the dressing in a small bowl and whisk together to combine.
On a nice serving plate start in the center and layer the zucchini in a round pattern and intersperse the rings of onion. Depending on the size of the plate and the zucchini, you may be able to make 2 layers. If you can make layers, sprinkle both a little cheese and a little dressing on the first layer before starting the second. Continue until all the onion and zucchini are used and then sprinkle the cheese and dressing over the top.