Step 1: Heat the oven to 180ºC. Grease and line a 23cm spring-clip cake tin. With your fingertips, rub together 50G BUTTER with the 50G FLOUR until the mix resembles breadcrumbs. Mix in the LIGHT BROWN SUGAR and set aside in the fridge.
Step 2: Cream together 225G BUTTER, softened, with the CASTOR SUGAR in a mixer (or with a hand-held mixer) until pale and fluffy. Gradually add the EGGS, then fold in the SELF-RAISING FLOUR, ALMONDS and BAKING POWDER. Transfer to the prepared tin.
Step 3: Arrange the APPLE SLICES on top, then scatter the BLACKBERRIES over; top with crumble mixture. Bake for 50 mins, or until a skewer inserted into the middle comes out clean. Leave on a wire rack for 5 mins, then turn out and serve warm with custard.
NOTE: Defrost and drain frozen berries well before adding to the cake.