140g golden caster sugar
140g unsalted butter, at room temperature
1 medium egg
200g plain flour
1 tsp baking powder
Preheat the oven to 160C / gas 4. Grease a 20cm springform cake tin and line the base with baking paper.
Heat the butter in a large pan then add the lemon zest, sugar and apples. Cook for 5 minutes to soften slightly.
Mix the arrowroot or cornflour with the lemon juice. Stir into the apple mixture with the blackberries, then transfer to a large plate and leave to cool.
To make the crumble, place the cold butter, flour and cinnamon into a food processor and blitz until you have fine breadcrumbs. Add the sugar and then blitz again.
To make the pastry, whisk the sugar and butter until light and fluffy. Beat in the egg, then add the flour and baking powder and mix to make a soft dough.
Scoop up the dough and place it in the base of the cake tin. Using your fingers spread the dough so it covers the base of the cake tin and about 4cm up the sides. It doesn’t have to look neat at this stage but if it is too soft to work with, then place the tin with the dough in the fridge for about 15 minutes to firm the dough up.
Spoon the apple and blackberry mixture in the centre of the tin and spread out.
Spoon the crumble mixture over the fruit and then scatter the oats on top.
Bake for about 40 minutes or until rise and golden brown. Leave in the tin to cool for a few minutes before removing.