Chop the cucumber and tomatoes into bite-sized pieces and add to a large mixing bowl. Slice the red onion into about 1.5-inch long slices and add to the bowl Slice the Kalamata olives in half and add to the bowl. Mix gently to combine. Set aside.
If you are not serving the salad immediately, or within an hour or so, transfer the veggies to a colander, set it inside a large bowl, and put the colander and bowl in the fridge until you're ready to finish the salad. This will help the moisture leach from the veggies.
Make the Dressing
Add all the ingredients to a squeeze bottle and shake vigorously to mix. If not using a squeeze bottle, add all the ingredients to a small bowl and whisk to combine. Season with Kosher salt and pepper to taste.
Finish the Salad
Squeeze or add about 2-3 tablespoons of the dressing to the cucumber and tomato mixture. Add more or less to suit your level of "dressed." Crumble the feta over the top of the salad. Serve and enjoy!!