Preheat the oven to 180 Celsius / 356 Fahrenheit.
Using an electric mixer, beat the eggs together with the mashed banana and melted butter until smooth.
In another bowl, stir together the dry ingredients - almond flour, erythritol or sweetener of choice, cinnamon and baking powder. Add to the bowl with the egg/banana/butter mix and blend until well-combined.
Last, stir in the crushed walnuts, reserving some to sprinkle over the top of the bread.
Line a small (7 x 3.5 inch / 1 lb) loaf tin with parchment paper and fill in the dough. Sprinkle the leftover walnuts on the top.
Bake for approximately 40 minutes or until a knife inserted comes out clean. Check the cake at minute 30. If the top is already brown enough, loosely place aluminium foil over it so it does not burn.
Let the banana bread cool completely before slicing.
