Clean and slice the celery, including the greens, and place in a bowl, add olive oil, salt, pepper and vinegar (to taste).
Peel and dice the onion, add to the celery and mix well so that everything can flow well.
Wash the tomatoes, pat dry, cut in half (max. Quarter), add to the celery and onion mixture and stir in well. Let everything steep again for a few minutes.