Start by washing the cucumbers and tomatoes thoroughly under cold running water. Pat them dry with a clean kitchen towel. Trim the ends of the cucumbers and then slice them into thin rounds. Slice the tomatoes into wedges or bite-sized pieces.
Peel the red onion and cut it in half. Slice it thinly into half-moon shapes. If you find the onion flavor too strong, you can soak the sliced onion in cold water for about 10 minutes to mellow out the taste. Drain and pat dry before adding it to the salad.
In a separate small bowl, whisk together the extra-virgin olive oil, red wine vinegar, dill, salt, and pepper. The red wine vinegar adds a tangy acidity to the salad while the dill enhances the flavors. Adjust the seasoning to suit your taste preferences.
Drizzle the dressing over the salad ingredients in the bowl. Gently toss the vegetables with the dressing to ensure an even coating. Allow the salad to marinate for about 10-15 minutes to let the flavors meld together. This will also allow the vegetables to absorb the dressing.