Add the ketchup and beef broth. Stir to combine. Scrape the bottom of the pot with a wooded spoon, to make sure bits are not stuck to it.
Add pasta and stir to combine.
Cover and seal the lid. Make sure the valve points to Sealed. Change setting to manual and adjust time to 5 minutes on High Pressure.
Once Instant Pot beeps to show that it's done, do a quick release, by changing the position of the valve to Vent. Carefully remove cover and stir.

Turn off the Instant Pot.
Top with cheese, put the lid back on but don't seal. Allow a minute or two for cheese to start to melt. Stir to combine.
Serve!