In a large pot or the Ninja Foodi inner pot, add the peeled bananas, lemon juice, water, and powdered pectin. Turn the heat on high and cook while mashing the bananas. You could also blend the ingredients in a blender and then pour into the pot.
Bring the mixture to a boil that cannot be stirred down. This takes anywhere from 5-10 minutes. You can adjust your heat down if you are afraid of scorching the mixture. Stir occasionally while boiling.
Once the mixture is boiling and continues to boil as you stir, add in the sugar and stir to combine.
Bring the mixture back to a boil that cannot be stirred down, this can take anywhere from 5-10 minutes. I use a thermometer and when the mixture reaches 220℉/104℃, it's done. See post if you don't have a thermometer.
Turn the heat off and stir until the banana jam is no longer boiling. Add in vanilla and cardamom. Stir to combine. Let the jam cool slightly in the pot.
Transfer to jars or another container that want to store the jam in. Refrigerate for at least 4 hours.
Serve & Enjoy!