Preheat oven to 180 degrees C. Grease and flour three 20cm round cake tins.
Dissolve the bicarb soda in the buttermilk.
Combine the sugar, 3 1/2 cups of the flour, ground nutmeg, ground cloves, ground cinnamon and the butter. Stir in the buttermilk mixture.
Toss the blackberries and raisins with the remaining 1/2 cup of flour to coat. Mix in the blackberries and the raisins into the batter and stir until evenly distributed. Pour batter into the prepared tins.
Bake for 25 to 35 minutes or until a toothpick inserted near the centre of the cakes comes out clean.