Cook the Pasta: Bring a large pot of salted water to a boil. Cook the tri-color rotini according to the package directions for al dente.
Cool it Down: Drain the pasta immediately and rinse it thoroughly under cold running water. This stops the cooking process and keeps your pasta from getting mushy.
Assemble the Base: Toss the cooled pasta into a large, pretty serving bowl.
Add the Mix-ins: Gently fold in the halved cherry tomatoes, fresh mozzarella pearls, sliced black olives, and diced red onion.
Dress It Up: Pour the Italian dressing over the salad. Give it a good, thorough toss until every single piece of pasta is beautifully coated. Taste it, then add a pinch of salt and pepper as needed.
Chill and Serve: Cover the bowl tightly and pop it into the refrigerator for at least 30 minutes. When you are ready to serve, give it one more quick toss and top with fresh basil if you want a little extra pop of green.