Thinly slice the cucumber into 1/8-inch rounds and cut the tomatoes into 1/2-inch wedges, placing them in a large mixing bowl as you go. Thinly slice the red onion and add it to the bowl. This prep work ensures all vegetables are evenly sized for consistent texture and flavor throughout the salad.

In a small bowl, whisk together the olive oil, apple cider vinegar, dried oregano, granulated sugar, sea salt, and black pepper until the sugar and salt are fully dissolved and the dressing is well emulsified. I like to taste the vinaigrette before adding it to the vegetables—this way you can adjust the seasoning to your preference without having to remix the whole salad.

Pour the vinaigrette from Step 2 over the prepared vegetables from Step 1 and gently toss to coat everything evenly. Sprinkle the fresh parsley over the top and give it one final gentle toss. Cover the bowl and refrigerate for at least 20 minutes—this allows the flavors to meld and the vegetables to soften slightly while keeping their crunch. I find the salad tastes even better after 30-40 minutes, so if you have time, let it sit a bit longer.