Wash the romaine lettuce and kale under cold running water. Pat them dry and chop the romaine into bite-sized pieces, tearing the kale into smaller pieces.

Combine the chopped romaine and kale in a large salad bowl.

Fold in the diced cucumber, halved cherry tomatoes, and sliced red onion.

Sprinkle the shredded Parmesan over the top of the salad.

In a small bowl, whisk together the olive oil, red wine vinegar, salt, and pepper.

Drizzle the dressing over the salad and toss gently to coat.

Taste and adjust seasoning if needed. Serve immediately.