Prepare 6-inch cake pan by lining with parchment paper, or grease and flour.
Combine banana and sour cream. Set aside. In a large bowl, cream together the butter and sugar until smooth. Beat in the egg, then stir in the vanilla and banana mixture.
½ cup mashed ripe banana, ½ cup sour cream, 2 tablespoons butter, ⅔ cup white sugar, 1 egg, ½ teaspoon vanilla extract
Combine the flour, baking soda, baking powder and salt; stir into the banana mixture. Spread the batter evenly into the prepared pan.
1 cup flour, ½ teaspoon baking soda, ½ teaspoon baking powder, ⅛ teaspoon salt
Use the Bake setting on the air fryer lid. Set the cycle for 30 minutes at 325F, with the cake pan uncovered. Remove pan, cover with foil and return to the Instant Pot. Bake again for 25 minutes covered at 325F. When done, a toothpick inserted in the center should come out clean.
Allow to cool in pan for 15 minutes, then remove and finish cooling on a wire rack.