Mix the diced onion with the apple vinegar and leave to stand for a couple of minutes while you prep the rest. I will take the sharpness of the onion.
Mix all the other ingredients together. Remove the onion from the vinegar and add to the salad. Make the dressing by combining all ingredients, use the apple vinegar from the onions, and mixing it well.
Pour the dressing over the salad and leave to stand for a bit so the flavors can develop.