Preheat the oven to 160˚C. Line and grease a 500g cake tin.
Place the butter and sugar into a mixing bowl and mix until light and fluffy.
Next, add in the eggs, start to combine and sprinkle over the flour.
Stir until thoroughly combined then fold in the apple pieces and blackberries.
Pour half into the prepared tin and sprinkle with the half of the crumble mixture.
Add the rest of the cake batter and top with the leftover of crumble mixture.
Place in a preheated oven and bake for 45-50 minutes or until a skewer inserted in the centre comes out clean.
Remove from the oven and allow to rest for 5 minutes.
Leave to cool and enjoy within the day or store in a clean container for a few days in the fridge.