Preheat the oven to 350F and grease a 7 or 8" springform pan with non stick spray.
In a large bowl, mash the banana with a fork then add in the melted butter, egg, egg yolk, and vanilla. Stir until well combined.
In a separate bowl, combine the almond flour, flax meal, erythritol (or other sweetener), salt and baking powder. Stir until it's all mixed together.
Gradually combine the dry ingredients with the wet, stirring after each addition, until they are well incorporated.
Transfer batter to your prepared pan pan, and bake 10-15 minutes, taking it out when it is still slightly underdone
For the cheesecake
In a large bowl, combine the cream cheese and erythritol using an electric hand mixer, until smooth and creamy. Add in the vanilla, sour cream, and heavy cream and mix until well combined.
Add the egg, and mix just until combined. Be careful not to over mix the egg, as it will change the texture of the cheesecake.
Pour this mixture into pan, on top of prepared crust
Cook the cheesecake (Instant Pot)
Wrap the cheesecake with foil – crimping around the edges so that it stays secure.
Pour 1 ½ cups of water into the inner liner of your instant pot and place the trivet in the bottom, keeping the handles folded up.
Fold a large piece of aluminum foil (about 2 feet) 4 times to make a sling that you will use to lift the cheesecake out of the IP when its done cooking.
Lay the sling out, and set the cheesecake on top of it, centered. Gather up the two ends and carefully lift the pan, and set it into the instant pot. Leave the sling in place, just folding the edges over.
Secure the lid on your instant pot and set the steam vent to the sealing position.
Press “manual” and then the + or – button to adjust the time to 30 minutes. (make sure it is set to HIGH pressure)
When cooking cycle ends, allow pressure to naturally release and carefully remove cheesecake from pot using the sling.
Leave it covered for about 30 minutes, then carefully peel off the foil. Let it sit at room temp for about 1 hour, then refrigerate for about 4 hours before serving or removing from spring form pan (tough, I know!)
Cook the cheesecake (oven)
Preheat oven to 400°F. Place a large pan filled with ½ inch of water in the oven.
Carefully place cheesecake into preheated water bath in oven. Bake for 10 minutes, then turn the oven down to 350°F and bake for 25-30 minutes or until top is browned and the cheesecake is only slightly jiggly. Remove from oven and allow to sit at room temp for 1 hour, then in chill in the refrigerator for at least 4 hours before serving or removing from spring form pan.