Cut the cucumber long ways into quarters and then cut into slices (they will look like mini triangles)
Dice the tomatoes. If using cherry tomatoes we cut into quarters.
Dice onion (Optional)
Toss all of these into a bowl.
Mix the dressing (oil, vinegar, salt, pepper, water) and pour over the vegetables.
We like to cover and marinate these for about an hour before we eat them.