Preheat oven to 350 degrees Fahrenheit.
Prepare a loaf pan by spraying with non-stick spray or a coating of butter with a dusting of flour. Whichever way you prefer to prepare baking pans. Set aside.
In a small bowl, mix together the flour, salt, baking soda, and cinnamon. Set aside.
In a large glass bowl, mix together the butter and sugar with a hand mixer until it's fully combined and has a soft, fluffy texture.
Next, add in the yogurt, sourdough starter and vanilla extract. Mix well with a hand mixer until everything is fully combined.
Add in eggs and mix again with the hand mixer just until they are fully incorporated. Don't overmix.
In a medium bowl mash bananas with a fork until they are a creamy consistency. Some smaller lumps are okay. The softer the bananas are the easier they will be to mash.
With a wooden spoon or spatula, fold in the mashed bananas just until everything is fully incorporated.
Dump in the flour mixture, and with a wooden spoon, fold everything together until the flour is fully incorporated. Use a spoon or spatula at this point because we don't want to overmix the batter. That can lead to a dense texture.
Pour the batter into the prepared loaf pan and using a spoon or spatula scrape the bottom of the bowl so all the batter makes it in the pan.
Give the pan a good shake so the batter settles and is evenly distributed.
Place pan in the oven and bake for 55-60 minutes.
About halfway through if the top of the bread starts to turn brown, make a tent out of tin foil and place it over the top. This will allow the inside of the bread to continue to cook but will protect the top from burning.
The bread is done when a toothpick is inserted in the middle and comes out clean.
When done, place the pan on a cooling rack and allow the bread to cool inside the pan for 10 minutes.
Take a knife and run it between the bread and the side of the pan. Just to get any piece that may be stuck.
Remove loaf from the pan and allow it to cool.
Slice and serve with a little butter and enjoy!