Grease a 6-inch cake pan or springform. Line the bottom with parchment if you want to be extra safe.
In a medium bowl, mash bananas, then whisk in sugar, egg, oil, and vanilla until combined.
Sprinkle in flour, baking powder, baking soda, cinnamon, and salt. Stir until just mixed—don’t overwork it.
Fold in chocolate chips (if using).
Pour batter into prepared pan. Cover tightly with foil.
Add 1 cup water to the Instant Pot. Place cake on a trivet inside the pot.
Cook on High Pressure for 35 minutes, then natural release for 10 minutes. Quick release remaining pressure.
Let cool completely before slicing.
