Preheat the oven to 350°F (175°C). Grease a 9x5-inch loaf pan.
In a medium bowl, whisk together flour, baking soda, and salt.
In a large bowl, mix melted butter with sugar until combined. Beat in eggs one at a time, then stir in vanilla extract.
Add mashed bananas to the wet ingredients and mix until combined.
Gradually add the dry ingredients to the wet ingredients and stir just until combined. Do not overmix.
Pour half of the batter into the prepared loaf pan. Drop spoonfuls of Nutella over the batter and gently swirl with a knife. Pour remaining batter on top and swirl again.
Bake for 50 minutes or until a toothpick inserted in the center comes out clean.
Allow the bread to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.
Notes
Serve with butter or a dusting of powdered sugar for extra indulgence.