Slice the red onion into thin 1/8-inch half-moons and place them in a bowl with ice water and 1 tablespoon of the red wine vinegar. Let soak for 10 minutes—this mellows the onion's sharp bite and makes it crisp and refreshing. While the onion soaks, prepare all other vegetables.

While the onion soaks, cut the tomatoes into wedges or chunks, then slice the cucumber into 1/2-inch thick semi-circles (partially peel in strips first for visual appeal). Dice the green bell pepper into bite-sized pieces. Crumble or cut the feta cheese into large chunks—I prefer leaving it in substantial pieces rather than crumbling it fine, as it holds better in the salad. Chop the fresh mint and have all ingredients ready to assemble.

In a large shallow dish or platter, arrange the tomatoes, cucumber, bell pepper, and olives in a pleasing pattern—this is a rustic salad, so don't overthink it, just keep vegetables somewhat organized. Drain the soaked red onion well and scatter it over the vegetables. In a small bowl, whisk together the olive oil, remaining red wine vinegar, salt, and black pepper. Drizzle this dressing over the entire salad and sprinkle with half of the oregano, then toss gently to combine. I like to let it sit for a few minutes after dressing so the flavors can meld together.

Arrange the feta cheese chunks over the top of the dressed salad, creating an attractive presentation. Sprinkle the remaining oregano over the feta, then scatter the chopped fresh mint across the entire salad. Serve immediately at room temperature—this is how horiatiki is traditionally enjoyed, allowing all the fresh flavors to shine without being chilled.