Wash and dry the cucumbers. If using English cucumbers, leave the skin on; if using regular cucumbers, peel partially or fully. Slice into half-moons about 1/4-inch thick.
Halve the cherry tomatoes and thinly slice the red onion.
In a large bowl, combine the sliced cucumbers, halved tomatoes, sliced onion, olives (if using), and torn basil.
Pour the Italian dressing over the salad and toss gently to coat all ingredients evenly.
Let the salad sit at room temperature for 10 minutes to allow flavors to meld.
Taste and adjust seasoning with additional salt or pepper if needed. Serve at room temperature or chilled.