Wash, halve and stone the plums. Put the amamrettini in a freezer bag and crumble finely with a cake roll. Stir in the eggs one by one.
Add milk and liqueur and stir in. Mix flour and baking powder, stir in. Stir in Amarettini. Pour the dough onto a greased baking tray and spread smooth. Spread plums on top. Sprinkle with almonds and bake in the preheated oven (electric: 175 °C/ gas: level 2) for 40-45 minutes.
Let the plum cake cool down. Dust with icing sugar.