Spread a small amount of pesto on inside of butterflied chicken. Add slices of tomato. Sprinkle with half the mozzarella cheese. Close chicken (will be "stuffed").
Spread pesto on top of chicken.
Spread any remainder pesto in bottom of Instant Pot. Add water or chicken broth. Carefully place stuffed chicken in bottom of pot.
Sprinkle parmesan cheese on top of chicken.
Secure lid on Instant Pot. Flip vent to sealed.
Cook on HIGH pressure for 7-8 minutes. Once done do a quick release.
Add cherry tomatoes on top and remaining mozzarella cheese.
Close lid again. Set vent to sealed. Cook for an ADDITIONAL 2 minutes on HIGH pressure. When done let natural release for 10 minutes. The internal temperature of chicken needs to reach 165°F.
Serve with noodles or spaghetti squash if desired.
**Due to the nature of pressure cooking there is always room for inconsistency. The times given here are based on 4-5 servings fresh. If you are using more servings you may need to increase your cooking time.**