Set Instant Pot to sauté mode. Add butter and let melt, then add garlic and onion. Sauté for 3-4 minutes.
Add chicken and stir. Cook until no longer translucent, about 5 minutes. Add in rice, broth, and lemon juice. Stir well, bringing chicken pieces to top.
Secure lid on pot and set valve to Sealing. Set to Manual High Pressure for 8 minutes.
When cook time is completed, let naturally release for 2 minutes, then carefully Quick Release remaining pressure. Stir well and season with parmesan, salt, and pepper to taste. Add a little more chicken broth, if desired, to reach desired consistency - optional.
If you find liquid still remaining on the top of your Instant Pot chicken and rice after cooking, stir well and turn on Sauté mode to fully incorporate.