Turn Instant Pot on to Saute. Begin to heat olive oil.
Add minced garlic, chopped onion and red bell pepper. Continue to saute until tender.
Turn off the Saute function. Add tortellini and water.
Top with 2 cups of marinara sauce.
Close Instant Pot, seal pressure release valve. Cook on high pressure for 3 minutes.
Once cooking time is complete, quick release the pressure.
Open and add the remaining marinara sauce from the jar. Stir tortellini well, making sure everything is evenly coated. Let it cool for a few minutes.
Top with shredded Parmesan cheese, if desired.