Preheat the oven to 350°F. Spray a loaf pan with nonstick cooking spray.

Melt butter in microwave in a large mixing bowl. Add the bananas, mash with back of spoon, and mix to combine.

Stir in the sugar, egg, and vanilla. Sprinkle the baking soda and salt over the mixture and mix in.

Add in the flour and stir until incorporated.

Scoop the chocolate hazelnut spread into a microwave safe bowl. Heat at 50% power in 30 second intervals until melted.

Pour half of the banana mixture into prepared loaf pan. pour half the melted spread across the top. Add the remainder of the batter, then top with the rest of the chocolate spread. Use a knife to swirl the Nutella and banana mixture together.

Bake for 50-55 minutes, or until a wooden toothpick comes out clean when inserted. Cover the bread if it begins to get too brown on top. Cool to warm before serving.