Place rotini in the Instant Pot and stir in the 2 1/2 cups water, salad dressing, garlic, and Italian Seasoning.

Secure lid and seal pressure release vent.

Set Instant Pot to Pressure Cook on High pressure for 5 min.

Once cook time has elapsed, carefully perform a Quick Release of the pressure.

Immediately stir in ice water and ice to cool the pasta down. No need to drain.

Fold in black olives, mazzarella cheese, grape tomatoes, Parmesan cheese, and red onion before seasoning with salt and pepper to taste.

Cover and refrigerate at least 1 hr. before serving.