Slice tomatoes into wedges and then cut in half crosswise. Toss them with 1/4 teaspoon of salt, and place in a colander to drain for 30 minutes.
Place sliced onion in a bowl of iced water for 15 minutes.
Whisk lemon juice with oregano, 1/4 teaspoon salt, and pepper in a small bowl.
Chop cucumber into 3/4 inch wedges.
After 30 minutes, transfer the tomatoes into a large bowl. Add cucumber, olives, and capers and toss with the lemon juice mixture. Drizzle with two tablespoons of oil and toss everything gently together. Adjust salt and pepper to taste.
Cut feta into two individual two-ounce portions in a rectangular or triangular shape.
Divide the salad mixture between two serving plates and top each one with a portion of feta.
Season feta with an extra sprinkle of oregano and drizzle with the remaining 1/2 tablespoon of olive oil. Enjoy!