Mix pesto, olive oil, salt, garlic powder, black pepper, and balsamic vinegar in a bowl. You can add more balsamic to taste but it will start to change the color of the dressing unless you are using white balsamic vinegar.
Add pasta and toss to coat. Fold in tomatoes, mozzarella, and fresh basil.
Chill in the fridge until ready to eat. Drizzle with balsamic glaze if desired.
Source: slightly adapted from Allrecipes