Prepare the vegetables by washing and dicing them.
Soak the onion in cold water for 10 minutes.
In a large bowl, combine the diced cucumbers, tomatoes, and drained red onion.
In a separate bowl, whisk together the Greek yogurt, olive oil, vinegar, salt, pepper, and chopped dill.
Pour the dressing over the vegetable mixture and toss gently to combine.
Taste and adjust seasoning if necessary.
Chill the salad in the refrigerator for at least 30 minutes before serving.
Serve chilled, garnished with extra dill if desired.