Preheat your oven to 350°F (175°C) and grease a loaf pan or line it with parchment paper.

Mash the ripe bananas in a large bowl until smooth, leaving some lumps for texture.

Stir in the melted butter until well combined.

Add in the eggs and vanilla extract, mixing well until fully combined.

In a separate bowl, whisk together the flour, sugar, and baking powder.

Gradually fold the dry ingredients into the wet mixture until just combined.

Warm the Nutella in the microwave for 15 seconds to soften.

Pour half the batter into the loaf pan, dollop warmed Nutella on top, then swirl with a knife. Repeat with remaining batter and Nutella.

Bake for 55-65 minutes, checking for doneness with a toothpick.

Let it cool in the pan for 10 minutes before transferring to a wire rack to cool completely.