A wonderful cake that is easy to prepare but hard to resist.
- Place the butter and both types of sugar into the bowl of a food processor. Attach the flat beater and mix on speed 4 until the mixture is light and fluffy.
- Add the eggs and mix again at speed 4 for 30 seconds.
- Add the flour, salt, and baking powder. Turn the speed control to 4 and mix for another 30 seconds.
- Add the sour cream and mix again at speed 2 until well combined.
- Line a baking tin with parchment paper. Pour the batter into the tin.
- Cut the plums in half and remove the pits. Slice the plums and arrange them on the batter in a spiral pattern.
- Bake for 35–40 minutes until golden in a preheated oven at 175 °C (347 °F).
- Once the cake has cooled, dust it with icing sugar mixed with starch.