Begin by making the buttermilk - put the almond milk and lemon juice into a small bowl, stir and leave for 5-10 minutes to curdle
Meanwhile, preheat the oven 180C/ 350F/ GM4 and grease and line a deep-sided 8-inch springform cake tin with baking parchment
Take 1 teaspoon of the flour and toss the dried blueberries in it. Set aside
Pour the rest of the flour into a medium-sized mixing bowl along with the baking powder, baking soda, salt and sugar. Mix briefly with a balloon whisk
When the buttermilk has curdled stir in the oil and almond extract
Pour the wet ingredients into the dry and mix with the balloon whisk for around 1 minute until the batter is just smoothP
Pour ½ of the batter into the prepared tin and sprinkle ½ of the blueberries and ½ of the bilberry powder over it
Drizzle 3 tablespoons of the remaining batter over the cake (it won't cover it entirely). Add the remaining blueberries and bilberry powder
Spoon the remaining batter over the top and use the back of a teaspoon to ensure that all of the blueberries are covered. You might notice a few streaks of bilberry powder this is totally fine (it adds to the charm of the cake in fact)
Bake for 35-40 minutes until the cake is well risen, golden and a cocktail pick inserted into the centre comes out clean
Let the cake cool completely in the tin before unmolding carefully - the sponge is quite delicate, so remove the parchment carefully