Begin by thoroughly washing the cucumbers and radishes under cold running water. Slice the cucumbers into thin rounds, about 1/8 inch thick, and cut the radishes into quarters or thin slices.

In a small bowl, combine the olive oil, lemon juice, and sumac. Whisk together until well emulsified.

In a large mixing bowl, add the sliced cucumbers and radishes. Drizzle the dressing over the vegetables and gently toss until evenly coated.

Taste your salad and adjust seasoning with salt or lemon juice if needed.

For a fresher taste, chill the salad in the refrigerator for about 10 minutes.

Serve the salad chilled or at room temperature, either on individual plates or a large platter.