I went through trial and error and I am quite happy to share the result!
Ingredients(for 12 medium sized slices)
•2 medium ripe bananas, mashed
•2 tbsp of melted coconut oil
•1 tbsp of coconut oil (for greasing)
•2 + 1 tbsp of agave nectar
•1 tbsp of (real!) vanilla extract
•3 medium sized eggs
•100 g of almond flour
•50 g of coconut flour
•1 1/2 tsp of baking soda
•1/2 tsp of sea salt
•1 tsp of allspice
•40 g of chopped walnuts
What you do
•preheat the oven to 175°C
•grease a loaf pan of 12 x 28 cm with coconut oil
•in a blender, whip up the eggs and then reduce the speed and add the wet ingredients until everything is well combined
•mix the dry ingredients together first and then add to the wet mixture
•now pour everything into the baking loaf pan
(the mixture will be thick and you will need to smooth it evenly with a rubber spatula of the back of a tablespoon)
•now bathe the chopped walnuts with 1 tbs of agave and with your hand, sprinkle it evenly over the top
•place the loaf pan in the middle of the oven and bake for approximately 30 minutes (till the mixture is dry in the inside)
•why agave nectar instead of honey?
Agave nectar has a lower GI than honey and is therefore healthier for you
Honey will caramelize in the oven; this will make your cakes look dark in the inside and give it a bit of a 'burnt' aftertaste....
•what if you cannot find agave nectar in your region?
Try maple tree syrup if you are in North America; in South America I have experimented with lemon tree syrup and this works well too. You would think the citrus taste would be overwhelming but it is not...