1. Preheat the oven to 180°C (350°F). Line a 24cm springform tin* with baking parchment and set aside. Wash the plums, dry, remove the stones and cut them in half or into 4 slices. Set aside.

2. For the streusels add the flour, sugar, and cinnamon to a large bowl, mix until well combined. Add the butter and rub everything between your fingers until you get nice streusel. Place in the fridge until needed.

3. Add the flour for the batter to a large bowl, add the baking powder, sugar and oats, and mix. Add the soft butter, eggs, milk, and vanilla extract and mix until you get a well-combined batter. Transfer to the springform tin, smooth out the top and place the plums in a circular pattern on top. Sprinkle with the streusel and bake for about 50 minutes until done. Take it out of the oven and let it cool down on a wire rack. When cooled, remove from the tin and serve with some whipped cream or vanilla sauce.