Directions

1. Preheat the oven to 325 degrees F. Generously coat an 8 1/2-inch-by-4 1/2-inch loaf pan with nonstick spray and dust with flour, tap out the excess.
2. Whisk together the flour, baking soda and salt in a medium bowl and set aside. Mash the sugar with the bananas in a large bowl until smooth. Whisk in the butter, vanilla and eggs. Whisk in the flour mixture until just combined. 
3. Microwave the chocolate-hazelnut spread in a small microwave-safe bowl and until pourable, about 30 seconds. Reserve 2 tablespoons in a small bowl and set aside. Spread half of the batter in the bottom of the prepared pan. Pour the warmed hazelnut spread down the center of the batter leaving about a 1/2-inch border all around so that you have a chocolate-hazelnut center. Spread the remaining batter on top and smooth out with a spatula. 
4. Bake until the top is domed, about 1 hour 15 minutes. Cool in the pan and on a wire rack for 30 minutes, then carefully invert onto a platter or cake stand and then turn upright. Cool completely on the wire rack, about 1 hour. Microwave the reserved hazelnut spread until it can be drizzled, about 30 seconds. Drizzle the spread over the cake then sprinkle the hazelnuts down the center.