01 - Preheat oven to 350°F. Grease and flour a 9 x 5 inch loaf pan or line with parchment paper.
02 - In a large bowl, whisk together mashed bananas and melted butter until well combined. Add sugar, eggs, and vanilla extract; mix until smooth and creamy.
03 - In a separate bowl, sift together flour, baking soda, and salt. Gradually add dry ingredients to wet mixture and stir just until combined—avoid overmixing to ensure tender texture.
04 - In a small bowl, combine granulated sugar and ground cinnamon; mix thoroughly.
05 - Pour half of the batter into prepared loaf pan. Sprinkle half of cinnamon sugar mixture evenly over batter. Add remaining batter and top with rest of cinnamon sugar.
06 - Run a knife through batter in gentle swirling motions to create a marbled cinnamon ribbon effect throughout.
07 - Bake for 50–60 minutes until a toothpick inserted in center comes out clean. Check at 50 minutes to prevent overbrowning.
08 - Allow bread to cool in pan for 10 minutes, then transfer to wire rack to cool completely before slicing.