Plum and Blackberry Crumble Cake

Late summer brings a harvest of dark red plums and lustrous blackberries to the kitchen. A month or so earlier I make this cake with apricots and blueberries. Crushed amaretti biscuits and flaked almonds form the crumble – a satisfyingly crisp foil to the baked fruit. The cake is nicest served warm with crème fraîche or vanilla ice-cream.