Begin by bringing a large pot of salted water to a rolling boil over high heat. Carefully add fresh tortellini and cook according to package instructions (about 3-5 minutes) until al dente. Drain and spread out on a baking sheet to cool, drizzling with olive oil.

While tortellini cools, chop cherry tomatoes in half and slice red onion thinly. Soak onion in cold water for a few minutes, then gather ingredients in a large mixing bowl.

In the same bowl, combine the cooled tortellini, halved cherry tomatoes, and drained red onion. Add mozzarella pearls (if using) and pesto, gently folding the mixture until evenly coated.

Incorporate baby arugula and torn fresh basil leaves into the salad, folding them in gently.

Sprinkle grated Parmesan cheese over the top (optional) and give the salad one last gentle toss. Serve immediately or refrigerate for up to 2 hours.