Grease a large sponge cake/sweet bread pan with a little olive oil.
In a medium bowl, mix the flour, baking powder and salt; set aside.
In a large bowl, mix the sugar, oil, eggs and vanilla extract using an electric hand mixer.
Add the mashed bananas and mix to incorporate.
Add the flour mixture to the wet ingredients and mix until completely combined.
Using a rubber spatula, fold in the walnuts.
Pour the batter into the pan.
Bake for approx. 45 minutes, or until it passes the toothpick test.
Let the bread cool for 10 minutes in the pan, then transfer it to a cooling rack. Slice only when it is completely cool.
Notes
Store, well wrapped, at room temperature for up to 3 days or refrigerate for up to a week. Vegetarian (contains eggs); for a vegan version replace the 2 eggs with 2 flax eggs (2 Tbsp ground flaxseed + 6 Tbsp water).