In a bowl mash up the bananas with a fork or potato masher. You can leave some clumps of bananas or mash it up all the way.
Add in the sugar, vanilla extract and the egg and whisk very well. You will then add in the yogurt and the melted butter. Give it another good whisk to incorporate the ingredients well.
In another bowl, mix the dry ingredients together; that being the flower, baking powder, baking soda, cinnamon powder and a pinch of salt. Give it a stir and pour over the wet ingredient. Fold everything together to obtain nice and smooth batter mixture.
Line some cupcake/muffin liners in a muffin pan. Using an ice-cream scoop, scoop in one scoop of the batter into each muffin cup. You can then add in a teaspoon of Nutella spread into each muffin cup and swirl around with a wooden skewer or toothpick.
Place and bake in a 375 degree preheated oven for 20 minutes until the muffins are gold and brown on the top. Remove and let it cool before serving.