Dice the cucumber and tomatoes into uniform bite-size pieces (about ½-inch cubes). For the best texture, remove the seeds from the cucumbers if they're large or watery.
Thinly slice the red onion into half-moons. If the onion flavor is too strong, soak the slices in cold water for 5-10 minutes, then drain and pat dry.
Chop the parsley and mint very finely.
In a small bowl, whisk together lemon juice, extra-virgin olive oil, salt, and black pepper until well combined.
In a large serving bowl, combine the diced cucumber, tomatoes, red onion, chopped parsley, and mint. Add optional bell pepper and chickpeas if using.
Pour the dressing over the vegetables and herbs and toss gently to coat evenly.
If using feta cheese, sprinkle it over the top just before serving.
For an authentic touch, dust with sumac if desired.
Serve immediately or chill for 15 minutes to allow flavors to meld.
