In a medium bowl whisk together flour, baking soda and salt.
In another bowl, whisk together eggs, sugar, vanilla, butter and bananas. Add in dry ingredients and mix just until combined.
Spoon and spread batter into a 10-inch cast iron skillet.
Place dollops of nutella over the top of the batter and use a knife to swirl it around.
Bake bread in preheated oven for 40 - 45 minutes or until a toothpick inserted comes out clean.
Transfer to a cooling rack to cool completely. Slice and serve.
Notes
When using a cast iron skillet, make sure that it is well seasoned or the bread may stick to the bottom. You can also grease it lightly with butter before adding the bread. If you prefer to make this in a loaf pan, you'll have to increase the cook time. I'd start checking the doneness at 55 minutes. Nutrition information for estimation purposes only.