There are only three vegetables that go into Tabouleh - tomatoes (beautiful jardin one), parsley and fresh mint (preferably from jardin).
You chop the parsley and mint really fine and mix with tomatoes diced into very tiny pieces. This becomes your base.
You chop white onion, sprinkle them with salt and pepper and put aside.
The idea is that salt and pepper does not necessarily go on all the vegetables, just mixed with the onions to give a subtle enhancement to the flavour and keep the fresh taste of vegetables prominent.
You soak a bit of bulgur wheat (not couscous, not quinoa, those will disqualify it from being called Tabouleh) in water and a sprinkle of lemon juice.
You then mix the vegetables, onions, olive oil and lemon juice to taste. Then add enough bulgur wheat to colour it but not overwhelm the parsley.
This is how an authentic Tabouleh will look like, anything else, as mentioned before, should not be called Tabouleh. Enjoy!