Preheat and prepare pan. Preheat oven to 350oF (180°C). Spray a 9x5” loaf pan with non-stick cooking spray or grease with butter and set aside.
Mash bananas. In a small mixing bowl, mash bananas with a fork. Set aside. 1 ½ cups (340 g) very ripe bananas (about 4 medium)
Combine dry ingredients. In a mixing bowl, whisk together flour, baking soda, and salt. 2 ½ cups (300 g) all-purpose flour 1 teaspoon baking soda 1 teaspoon salt
Combine wet ingredients. In the same mixing bowl with the bananas, whisk in the sugar, oil, eggs, sour cream 1 teaspoon vanilla extractand vanilla extract and stir until combined. 1 ¼ cups (248 g) granulated white sugar ½ cup (120 mL) canola oil 2 large eggs room temperature ½ cup (113 g) sour cream
Combine wet and dry ingredients. Add the dry ingredients to the wet ingredients and mix together with a spatula until just combined.
Swirl in Nutella. Microwave the chocolate hazelnut spread for 10-15 seconds so it softens and you can drizzle/spread it. Spoon half of the banana batter into the prepared pan. Drizzle on half of the nutella spread. Swirl with your knife. Repeat with remaining batter and spread. ½ cup (160 g) Nutella (chocolate hazelnut spread)
Bake. Bake for 60-65 minutes until a toothpick inserted in the center of the bread comes out clean. Remove from the oven and allow the bread to cool completely in the pan set on a wire cooling rack. Store the bread, and any leftovers, covered at room temperature for 2 days, or in the refrigerator for up to 1 week.