Wash the cherry tomatoes thoroughly and cut them in half.
Finely chop the onion and basil.
Mix olive oil, balsamic vinegar, salt, and pepper in a bowl.
Add the prepared cherry tomatoes, onion, and basil to the bowl.
Pour the marinade sauce over and toss well.
Let it marinate in the refrigerator for about 20 minutes.
Serve on a plate to finish.