Add the chopped romaine lettuce (2-3 cups), halved cherry tomatoes (1 pint), kalamata olives (1/2 cup), sliced cucumber, diced bell pepper, sliced red onion (1/4 cup), and crumbled feta cheese (6 oz.) to a large bowl. (If preparing ahead of time, stop here and refrigerate).
Just before serving, sprinkle the top of the salad with the kosher salt (1/2 teaspoon) and the black pepper (1/2 teaspoon), and drizzle with the olive oil (2 tablespoons) and red wine vinegar (1 tablespoon).
Mix the salad together until everything is coated and serve.
If you're sensitive to the acidity of vinegar, try 1/2 tablespoon or 2 teaspoons instead of a whole tablespoon. You can also make a separate dressing mixed with a little honey or sugar to temper the acidity, or use this method with a typically less acidic vinegar, like balsamic or cider vinegar, or with lemon juice.
For a dairy free version, omit the feta or replace it with a vegan substitute. Omit the feta to make this salad paleo/whole30 compliant.
To make ahead of time, you can prep the ingredients and assemble them in a bowl up to 24 hours in advance. Add the salt, pepper, oil, and vinegar just before serving, otherwise it will become quite soggy.