Combine olive oil, vinegar, oregano, lemon rind, and salt in a large bowl, stirring with a whisk. Add romaine lettuce, tomatoes, and onion; toss gently to coat.
The chopped romaine salad on the side was also a really good, solid, basic salad. The fresh oregano was the key! That I would make again if needing something simple with ingredients I usually have on hand.
