Arrange a rack in the center of the oven and preheat to 325°F. Lightly butter and flour your loaf pan of choice. This recipe will make one standard loaf or three mini 6 inch x 3 inch loaves.
In a large bowl, sift together the flour, baking soda, baking powder, cinnamon, and salt. Set aside.
In another large bowl, use a whisk to whisk together the eggs and sugar until light and fluffy. If desired, use a stand mixer fitted with the whip attachment and whip until light and fluffy. Slowly drizzle in the oil and whisk to combine completely.
Stir in the mashed bananas, sour cream, and vanilla until combined.
Fold in the sifted flour mix, using a rubber spatula, ensuring there are no lumps of flour or flour streaks.
Pour the batter into your prepared pan and bake for 1 hour and 15 minutes for a standard loaf and 50 minutes for mini loaves. Insert a skewer into the center of the loaf. If the skewer comes out clean or with a few crumbs, the loaf is ready. If the skewer comes out coated with batter, bake for 5-10 more minutes. The top of the loaf should be golden brown and spring back when you press it.
Remove the loaf from the oven and let cool in the pan on a wire rack for 30 minutes, then remove from the pan and let cool completely on the wire rack before slicing. Enjoy!