Click sauté on Instant Pot and add butter.
Once butter has melted, add in the onions and garlic and sauté for about 5 minutes.
Turn sauté function off and add in the red bell pepper, seasoned salt, paprika, basil, and red pepper flakes.
Add in the chicken and season with desired amount of salt and pepper.
Pour in the chicken broth.
Place the spaghetti noodles in a single layer on top of the chicken and ensure they are fully submerged in the broth.
Secure lid onto Instant Pot and move valve to sealing position.
Cook manual high pressure for 6 minutes followed by a quick release.
Once pressure has released and pin has dropped, open the lid and stir in the half & half, cheddar cheese, and cornstarch.
Move Instant Pot to sauté function once more and stir everything together.
Allow to sauté for about 5 minutes, to allow sauce to thicken.
Turn off Instant Pot and serve warm! Enjoy!