Wash all vegetables thoroughly and pat dry.
Cut tomatoes into wedges or chunks about 1-inch in size and place in a large serving bowl. Sprinkle with a pinch of salt.
Slice cucumber into half-moons about ¼-inch thick and add to the bowl.
Add thinly sliced red onion, green bell pepper rings, and Kalamata olives to the bowl.
Gently toss the vegetables to combine them evenly.
Place the feta cheese on top of the salad in one large piece or as several large cubes.
In a small bowl, whisk together the olive oil, red wine vinegar, dried oregano, salt, pepper, and lemon juice (if using) until well combined.
Just before serving, drizzle the dressing over the salad and toss very lightly to coat, being careful not to break up the feta too much.
Allow the salad to rest for 5-10 minutes before serving to let the flavors meld together.