01 -
Fire up your oven to 350°F and grease a 9x5 loaf pan with a light coating of non-stick spray.
02 -
Toss flour, salt, and baking soda into a medium-sized bowl. Use a fork to stir things together. Put it to the side for now.
03 -
Using a mixer, whip up the butter and sugars in a large bowl on medium-high. Keep going for about 1–2 minutes until it looks smooth and fully blended.
04 -
Stir in the eggs, vanilla, and bananas. It's okay if a couple of banana chunks stick around—just scrape the bowl as needed.
05 -
Work the flour mix and sourdough starter gently into the wet mixture using your hands or a spoon.
06 -
Pour it all into your loaf pan and bake for about 55–65 minutes. When a toothpick poked in comes out with crumbs (not wet batter), it's good. Let the loaf cool for 10 minutes before slicing.