Preheat your oven to 350°F (175°C) and grease a loaf pan.
In a mixing bowl, mash the ripe bananas. Stir in the melted butter, baking soda, salt, sugar, beaten egg, and vanilla extract. Mix well.
Gradually add the all-purpose flour and mix until combined.
In a small bowl, mix the cinnamon and sugar for the swirl. Pour half of the batter into the loaf pan, sprinkle with half of the cinnamon-sugar mixture, then add the remaining batter and top with the rest of the mixture.
Bake in the preheated oven for 60 minutes or until a toothpick comes out clean.
Allow the bread to cool before slicing and serving.
Notes
For added flavor, you can include nuts or chocolate chips in the batter.