Ingredients :

• Cucumber — Choose thin-skinned cucumbers with few seeds — small Persian or Lebanese cucumbers are perfect. If using a classic thick-skinned cucumber, peel it halfway leaving strips for color, and remove seeds with a spoon. Otherwise, the salad becomes watery quickly.
• Tomatoes — Fleshy ones are preferred. Roma or Beefsteak tomatoes in summer, vine-ripened tomatoes out of season. Avoid cherry tomatoes here — they release too much juice and the texture becomes mushy. Ideal: a tomato that holds up well under the knife.
• Red onion — Red onion is less aggressive than white and brings a beautiful purple color to the bowl. If you find onions too strong, soak the rings for 10 minutes in cold water before adding them — it considerably softens the heat without losing the crunch.
• White wine vinegar — This is what makes the marinade. Basic white vinegar is too aggressive and flat. Apple cider vinegar works well too, with a light fruity note. Avoid balsamic vinegar — it colors everything and overpowers the vegetables.