Preheat your oven to 350°F (175°C) and grease a 9x5-inch loaf pan using butter or cooking spray.

In a large mixing bowl, mash 3 ripe bananas until mostly smooth, leaving a few lumps for texture.

Stir the melted 1/3 cup of butter into the mashed bananas until well combined.

Stir in 1 teaspoon of baking soda and 1/8 teaspoon of salt until evenly distributed.

Add 3/4 cup of sugar, 1 large beaten egg, and 1 teaspoon of vanilla extract to the mixture and stir until smooth.

Gradually fold in 1 cup of all-purpose flour, stirring gently to avoid overmixing.

In a separate bowl, mix together 1 tablespoon of ground cinnamon and 1/4 cup of brown sugar.

Pour half of the batter into the prepared loaf pan, followed by half of the cinnamon mixture, then layer the remaining batter and cinnamon blend.

Using a knife or skewer, gently create a zig-zag motion through the batter.

Bake for 60-65 minutes, or until a toothpick inserted comes out clean. Tent with foil if the top browns too quickly.

Let the banana bread cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.