1) In a large bowl, whisk together oil and vinegar and season with a big pinch of salt and pepper.
2) Run the tines of a fork down the side of a cucumber and chop into half rounds. Slice red onion into rough slices. Add cucumbers and onions to the bowl and toss to coat with dressing.
3) Roughly chop tomatoes and add to the bowl with any juice. Stir to combine.
4) Sprinkle fresh oregano over salad and season it to taste with salt and pepper. It’s best to let this sit for a bit before serving. Toss it together before serving and don’t be afraid to add another splash of vinegar.