Start by washing, pitting, and slicing the plums into wedges.
Preheat your oven to 180 °C conventional or 160 °C fan/convection.
250 g Butter, 120 g Sugar, 1 Egg, 420 g All-purpose flour, ½ Baking powder
For the streusel, add the cold cubed butter to the mixing bowl first, followed by all remaining streusel ingredients. Mix 10-15 sec. / Speed 6 until crumbs form (depending on whether you prefer fine or coarse streusel).
Line a small baking pan, approx. 30 cm x 20 cm, with parchment paper.
Press two-thirds of the streusel mixture firmly into the bottom of the pan to form your base.
Arrange the plum slices evenly over the base.
2 Eggs, 50 g Sugar, 25 g All-purpose flour, ½ Baking powder
Next, prepare the custard topping. Add all remaining ingredients to the mixing bowl, mix 10 sec. / Speed 4, and pour over the plums.
Finally, scatter the rest of the streusel over the top and bake on the wire rack in the lower third of the oven for 40-45 minutes.
Notes
Dust the cake with powdered sugar or serve with a generous dollop of whipped cream.
Feel free to swap out the plums for other fruits! Sweet cherries, damson plums, apples, or pears all work beautifully here.