In a bowl, mix together butter, eggs, and sugar until mixture is creamy. Stir in vanilla and banana.
In a separate bowl, mix remaining dry ingredients. Combine wet and dry ingredients until smooth. Pour mixture into a springform pan. Place steamer rack into the cooker with 1c of water. Lower spingform into the cooker and rest on top of rack.
Close and lock lid, set cooker to "Bake", and adjust for 45 minutes.
When done, quick release and make sure all pressure is released before opening lid.
Carefully open lid and carefully remove pan from the cooker. Allow to cool. Serve and enjoy.