Using a brush, coat the insides of your mason jars.
Divide up your filling and egg mixture into the mason jars.
Inside your Instant Pot, place your trivet into the pot with 1 cup of water on the bottom. Place the five mason jars on the trivet and place the lid on and seal.
Set the Instant Pot to manual high pressure for 8 minutes and then natural pressure release for 10 minutes before quick releasing the rest of the steam.
To serve, you can either pour out the frittatas onto a plate, eat it in the jar, or let them reach room temperature before placing their lids on and storing in your fridge for up to 5 days.