Preheat the oven to 350°F. Grease a 4x8-inch loaf pan with cooking spray or butter.
Mix all the dry ingredients - both flours, sugar, walnuts, baking soda, and salt till they are combined. Set aside.
In a mixing bowl, add the mashed bananas, coconut oil, yogurt, vanilla extract, and egg and mix them well. Add the flour mixture and mix them in till they are combined.
Pour the batter into the greased pan and bake for 50 - 60 minutes until a toothpick inserted in the center comes out clean. (I checked at the 50-minute mark and the banana bread was done)
Remove from the oven and let the bread cool in the pan for a few minutes before transferring it on a wire rack to cool completely.
Use a serrated knife to cut the bread into slices.
Instructions using a Blendtec Blender
Preheat the oven to 350°F. Grease a 4x8-inch loaf pan with cooking spray or butter.
Add mashed bananas, eggs, yogurt, coconut oil, vanilla extract, and sugar to the blender jar and secure the lid. Select "Batters" or blend on a Medium to Medium-Low speed for 30 seconds
Add the remaining ingredients - both flours, baking soda and salt in the blender and secure lid. Press "Pulse" 3–5 times or until dry ingredients are combined with the wet. Add walnuts (if using) to the mixture and press "Pulse" 2-3 times to combine.
Pour the batter into the greased pan and bake for 50 - 60 minutes until a toothpick inserted in the center comes out clean. (I checked at the 50-minute mark and the banana bread was done)
Remove from the oven and let the bread cool in the pan for a few minutes before transferring it to a wire rack to cool completely.
Use a serrated knife to cut the bread into slices.
Baking in Instant Pot
Grease a 6-inch bundt cake pan and pour the batter into the greased pan. Cover it with foil.
Add a cup of water in the steel insert of the Instant Pot. Place the trivet. Create a foil sling and place it on the trivet. Place the bundt pan and close the lid.
Adjust the pressure setting to high and the time to 40 minutes. Once the cooking is done, wait for 10 minutes before releasing pressure.
Carefully remove the bundt pan from the Instant Pot using the foil sling and let the cake cool in the pan before dusting it with powdered sugar.