Position a rack in the center of your oven, and preheat to 325°F. Grease a 9x5-inch loaf pan.
In a medium bowl, sift together the flour, baking soda, cinnamon, and salt. Set aside.
Using a stand mixer fitted with the whisk attachment, beat together the sugar and eggs on medium speed for about 5 minutes, or until light and fluffy. If using a hand mixer, beat for 8 minutes. If mixing by hand, whisk for about 10 minutes...or until your arm goes limp and you can’t be bothered anymore.
After your sugar and eggs have been properly mixed, reduce the mixing speed to low and slowly drizzle in the oil in a thin stream. This should take about 1 minute. This part is hard if you’ve only got a hand whisk, but do your best!
Add the bananas, sour cream, and vanilla extract. Mix on low speed just until combined.
Using a rubber spatula, gently fold in the dry ingredients until just incorporated (and there are no visible flour streaks). Avoid overworking the batter. Then fold in any add-ins (no more than ¾ cup total), if using.
Pour into the loaf pan, and pop it in the center of the oven. Bake for 60-75 minutes, until it’s a deep golden brown and the center springs back when you press it. Cool for at least 30 minutes.
This banana bread is great warm with butter, but in our opinion, it’s even better the next day. Cover, and let it sit on the counter overnight. We have a loaf pan that comes with a lid, so we just put that on. A cake plate with a cover also works well.