Pre-heat the oven to 180ºc /350 F. Grease a square 20×20 cm pan with melted coconut oil. Set aside.
In a medium sized bowl, mix the topping’s ingredients, adding only two tablespoons of coconut sugar instead of the four written above(you’ll use the remaining two tablespoons later).
Sift the dry ingredients into a large bowl. In a separate bowl, whisk together the wet ingredients. Pour the wet mixture over the dry one and mix slowly until everything’s well incorporated and you end up with a slightly thick batter.
Pour half of the cake batter into the bottom of the pan. Addone cup of blueberries on top, making sure to distribute them evenly. Add theremaining half of cake batter, followed by the last layer of blueberries. Tofinish things off, cover the cake with the coconut-walnut topping.
Bake the cake, in the pre-heated oven, for 45 minutes. After that time, take the cake out of the oven and scatter the remaining two tablespoons of coconut sugar on top of it – make sure you cover all the cake’s surface with the sugar, so that you end up with a crisp and caramelised layer. Return the cake to the oven for an additional 5 minutes. Once done, let it cool to room temperature, cut into squares and serve. Even though I like to eat it plain, it goes particularly well with coconut whipped cream.