Preheat the oven to 350°F and grease or line a 9×5-inch loaf pan with parchment paper.
In a large bowl, combine all of the dry ingredients (flour, sugar, salt, baking powder, and ground cinnamon if using). Whisk together until well combined.
In a separate bowl, peel and mash the bananas. Then add the eggs, oil, or melted butter, and vanilla extract. Whisk until well combined.
Pour the wet ingredients into the dry ingredients and use a rubber spatula or a large spoon to combine. This should not take very long, about 20 seconds. Do not overmix the batter.
Pour the batter into the prepared loaf pan and bake for 55-65 minutes, until a tester comes out with moist crumbs.
Remove the loaf from the pan and transfer to a cooling rack.