Preheat the oven to 180C/350F/Gas Mark 4. Line a 20 cm (8 inch) shallow square cake tin with a piece of non-stick baking paper a little larger than the tin, cut into the corners diagonally then press the paper into the tin so that the base and sides are lined.
Add sugar, flour and almonds to a large bowl then stir in the baking powder and cinnamon. Add the soft margarine and eggs and beat together with a wooden spoon until soft and creamy. Mix in the blackberries then spoon into the tin and level the surface.
Bake for 25-30 minutes until well risen, browned and the top springs back when pressed in the centre lightly with a fingertip. Leave the cake to cool for 10 minutes then lift out of the tin using the paper, transfer to a wire rack and leave to cool completely.
To decorate, beat the mascarpone and icing sugar together until soft and creamy. Stir in half the cinnamon then spread over the cake. Cut into 16 small squares; add a blackberry to the centre of each then sprinkle with the remaining cinnamon. Lift cakes off the paper and transfer to a serving plate.
Our thanks to Seasonal Berries for providing this recipe
Visit our baking section for more delicious cakes, biscuits and tarts