Cook the pasta in salted boiling water until al dente (about 8-10 minutes). Drain and cool under cold water.
While the pasta cools, chop the cherry tomatoes and slice the red onion.
In a large bowl, combine the cooled pasta, tomatoes, mozzarella, basil, and red onion.
In a small bowl or jar, whisk together balsamic vinegar, olive oil, salt, and pepper until well combined.
Pour the dressing over the salad and toss gently to combine.
Refrigerate for at least 30 minutes before serving to enhance flavors.
