Preheat your oven to 350°F (175°C). Grease a 9×5-inch loaf pan with butter or baking spray.
In a medium bowl, whisk together the flour, baking soda, salt, and cinnamon.
In a large mixing bowl or the bowl of a stand mixer fitted with the paddle attachment, beat the brown sugar and butter together on high speed until light and fluffy, about 3 minutes.
Beat in the eggs one at a time, stopping to scrape down the bowl between each addition. Mix in the vanilla extract.
Mix the mashed bananas into the wet mixture until just combined.
Add the dry ingredients to the wet mixture and fold together gently with a rubber spatula until just combined. Do not overmix.
Pour the batter into the prepared loaf pan and smooth the top.
Bake for 50 to 60 minutes, or until a wooden pick inserted into the center comes out clean.
Let the banana bread cool in the pan for 20 minutes, then remove it from the pan and let it finish cooling on a wire rack.