Place banana and Greek yogurt in a small food processor. Then process until smooth. Then, add in 2 giant handfuls of spinach and process again until smooth.Transfer into a large bowl and add the rest of the wet ingredients. Mix with a wooden spoon until smooth. Next, add in dry ingredients and mix.Spray your cupcake tin with coconut oil cooking spray. Fill muffins about ¾ of the way full.Bake at 350ºF for about 20 minutes or until the center is fully cooked.