Blueberry cake with buttermilk and cinnamon crumble

Preheat the oven to 180 °C. Line a baking dish of approx. 25 cm × 15 cm with baking paper.

In a small bowl, prepare the crumble: crumble together 90 g flour, 50 g sugar, 50 g butter, and 5 g cinnamon. Set aside.

In a large bowl, mix the dry ingredients for the batter: the remaining 170 g flour, 80 g sugar, and the baking powder. Add the egg, 150 ml buttermilk, and 30 ml rapeseed oil. Mix everything until smooth, then pour the batter into the prepared dish.