Prep the cucumber - Peel and deseed the cucumber. Slice vertically into 1/4-inch strips, the chop the strips across so that you have a 1/4-inch dice. Add to a medium bowl.
Prep the other veg and the lime and mix to combine - Mince the red onion. Destem and deseed the tomato, then chop it into a 1/4-inch dice. Chop the cilantro (stems and leaves) to yield 1/2 cup. Zest and juice the lime. Add the onion, tomato, cilantro, lime zest, lime juice, and Aleppo pepper to the bowl with the cucumber.
Finish - Drizzle with a bit of olive oil, and add salt and pepper to taste. Let rest for about an hour before serving.