(slightly adapted from "Heissgeliebtes Backen" by Annemarie Wildeisen and Florina Manz)
250g soft butter
1 tablespoon of vanilla extract
1 teaspoon baking powder
75g ground hazelnuts
a pinch of salt
if you like: one small piece of fresh ginger
For a cake tin of 30cm length or a round springform pan of 24cm diameter. I halved the above recipe and used a 18cm diameter springform pan.
Preheat the oven to 180°C, line your cake tin with parchment paper and grease with butter.
In a large bowl, mix butter with an electric hand mixer until soft and fluffy. Then, add sugar and beat again. Add vanilla extract and eggs and beat again until all is well combined.
In another bowl, mix flour, baking powder, salt and hazelnuts and add to your butter-egg-sugar mixture. Mix until all is well combine. Add some grated ginger (how much depends on your taste). Then, add your blackberries and mix with a ladle.
Fill your dough into the prepared cake tin and bake for about 50 minutes. A wooden skewer inserted into the cake should come out clean. If your cake browns too much towards the end of the baking time, cover with aluminium foil. Take out of the oven and let cool in the tin first. Then, release and let cool on a wire rack. Dust with icing sugar before serving.