Preheat your oven to 350°F (175°C) and grease a 9×5-inch loaf pan.

In a large mixing bowl, combine the mashed bananas and melted butter, stirring to combine.

Add in the sugar, beaten egg, and vanilla extract. Mix until smooth.

Sprinkle the baking soda and salt over the mixture and stir to combine.

Gently fold in the all-purpose flour until just incorporated; don’t overmix.

Pour half of the batter into the prepared loaf pan.

Drop spoonfuls of Nutella onto the batter, then add the remaining batter on top.

Use a knife to gently swirl the Nutella through the batter, creating a marbled effect.

Bake in the preheated oven for 50-60 minutes or until a toothpick inserted into the center comes out clean.

Once done, allow the bread to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.