Sift in the self raising flour and baking powder then fold into the mixture. Then add the zest and juice of the three limes, then fold into the mixture.
Pour into three 6 inch springform cake tins, lined with baking parchment and bake in the oven at 160c fan for 20-25 minutes until the sponge is light and springy to the touch.
Once the cakes are cooked and have cooled in the tin, take out and leave to cool for an extra 20 minutes on a wire rack.
For the Blackberry buttercream cream together butter and icing sugar and add the chopped up blackberries.
Layer throughout and on top of the cake and lastly top with blackberries - absolute heaven!
