Using non-stick baking spray with flour, lightly grease a 6 cup Bundt pan.
Using a large bowl, whisk together flour, baking soda, salt and sugar.
Add eggs, vegetable oil and sour cream. Stir well by hand. Do not use an electric mixer. You do not want to over mix the batter. Gently fold in the bananas and (walnuts if desired).
Pour the batter into the greased Bundt pan. Cover the Bundt pan with a piece of aluminum foil.
Pour two cups of water into the inner pot of the Instant Pot. Place the Bundt pan on the trivet that came with the Instant Pot. Lower the trivet and Bundt pan into the Instant Pot.
Place then lock the lid onto the Instant Pot. Point the steam release handle to sealing. Press the manual or the pressure cook button then set for 50 minutes at high pressure.When the timer sounds, allow for a 10 minute natural release then do a quick release to finish releasing the steam. Once the float valve has dropped, remove the lid.
Carefully remove the Bundt pan with the trivet from the Instant Pot. Remove foil.
Check for doneness: Insert a toothpick into the banana bread. It should come out with a few crumbs but be mostly clean.
Allow the banana bread to cool in the Bundt pan for 10 minutes. Then turn out onto a rack to finish cooling.
Store the banana bread tightly covered at room temperature for 3 - 4 days.