In salted boiling water, cook pasta according to package directions for al dente pasta. Drain and rinse with cold water until pasta is room temperature. Place pasta in a large bowl.
Add cherry tomatoes, pepperoni, onion, bell pepper, mozzarella, parmesan, and olives to the bowl. Set aside.
In a separate bowl, add olive oil, vinegar, italian seasoning, garlic powder, salt, pepper, and red pepper flakes. Whisk to combine.
Pour vinaigrette over pasta salad, then toss to coat. Refrigerate for 1 hour before serving.
If your pasta salad has been chilling for several hours/overnight and very cold, allow it to warm up slightly at room temperature for 20-30 minutes, then give it a toss to redistribute the dressing just before serving.
Pasta salad is best served the same day for freshest flavor. Pasta will continue to soak up dressing as it sits.
If your pasta salad has been sitting for a while and beginning to dry out, add a splash of olive oil and vinegar and toss to coat.
Vinaigrette can be substituted with your favorite bottled Italian dressing.
Leftovers will keep for 3-4 days in a tightly sealed container in the refrigerator.