Preheat oven to 180°C (350°F). Line a 20cm square cake tin with baking paper.
In a large bowl, combine sugar, flour and almond meal. Then stir through cinnamon and baking powder.
Add the soft margarine and eggs, and beat together with a wooden spoon until soft and creamy. Add the blackberries and mix through gently. Spoon into tin and level the surface as best as possible.
Bake for 25-30 minutes until the top springs back when pressed lightly in the centre with your fingertip. Remove from oven and allow to cool completely.
Beat the mascarpone and icing sugar until soft and creamy. Stir in the cinnamon, then spread over the cake (only when completely cooled). Decorate with blackberry coulis and drizzle over cake to serve.