Spray a 7x3-inch push pan with baking spray and set aside.
In a large mixing bowl, beat together with a hand mixer on medium speed mashed bananas, softened butter, and oil.
Add in both sugars and beat until combined.
Add the eggs, one at a time, and vanilla extract. Beat in the sour cream.
Add flour, baking soda, baking powder, salt, cinnamon, and nutmeg. Using a rubber spatula, mix just until combined.
Pour the batter into the prepared pan. Cover with foil.
Add 1 ½ cups water to the IP. Place cake pan on a trivet with handles and lower into the pot.
Lock the lid and make sure the vent valve is set to "sealing."
Cook on High Pressure for 55 minutes.
Allow pressure to naturally release for 15-20 minutes, then release the remaining pressure by turning the valve to "VENTING".
Remove pan by lifting the trivet out of the pot. Immediately remove the foil and allow the bread to cool in the pan for 15 minutes.
Remove the cake from the pan and cool on a cooling rack.
Consume within 3 days.