Preheat your oven to 350°F (175°C). Grease and flour a 9x5 inch loaf pan.
In a large bowl, whisk together the flour, baking soda, salt, and cinnamon.
In a separate bowl, cream together the softened butter and granulated sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the mashed bananas, sour cream, and vanilla extract until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix.
Pour the batter into the prepared loaf pan and spread evenly.
Bake for 55-65 minutes, or until a wooden skewer inserted into the center comes out clean.
Let the banana bread cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.
Notes
This banana bread is best served at room temperature. It can be stored in an airtight container at room temperature for up to 3 days, or frozen for longer storage.