Preheat oven to 350 and melt coconut oil, if necessary.
Mash bananas in the bowl of a stand mixer with the paddle attachment, or in a large bowl using a fork or potato masher.
Add eggs, vanilla, coconut oil, and sourdough starter. Mix well.
Mix flour, salt, and baking soda in separate bowl or lightly mix on top of the batter before stirring everything together using a wooden spoon. Don't overmix the wet and dry ingredients together.
Pour batter into a large, well-greased or parchment-lined loaf pan. Bake for 1 hour.
Allow to cool before slicing. It's delicious served with honey butter, or on its own. Enjoy!