Cut the tops of your bell peppers. Remove the seeds and membranes.
In a medium-size bowl, mix together the onion, ground turkey, cooked rice, salt, pepper, garlic, breadcrumbs, and half of the can of tomatoes, drained. You will use the tomato juice and remaining half can of tomatoes, so be sure to just set that aside.
Scoop the mixture into each of the bell peppers, filling up fully.
Add the water and the reserved half can of tomatoes, including the liquid, into your inner part of the instant pot. Place the trivet inside. Place the bell peppers on top of the trivet.
Lock the lid in place on your instant pot and set the sealing valve to sealed.
Set your instant pot to high-pressure for 8 minutes. Allow it to naturally release for 10 minutes, followed by a manual release.
Place the shredded mozzarella cheese on top of the meat mixture of your bell pepper. Close the lid on your instant pot and set to high-pressure for one more minute.
Once that minute is done, do a quick release.
Remove the bell peppers with tongs as they will be hot.