Ingredients

Step by step

1. You will need two 18cm round sponge tins, greased and base-lined with baking paper. Preheat the oven to 180°C, fan 160°C, gas 4. Put the butter and sugar in a mixing bowl and cream until really light and fluffy. Gradually add the beaten eggs a little at a time until creamy then gently mix in the flour with the lemon and lime zest and the lime juice to give a soft dropping consistency.
2. Divide the mixture evenly between the cake tins and bake for 25 minutes until just firm
   in the centre, golden brown and beginning to shrink from the sides of the tin.
3. Mix the rum and lime juice together and brush half this mixture over the hot cakes as soon as they come out of the oven. Allow to cool for 5 minutes in the tin then remove from the tins, turn upside down on a wire rack, peel off the lining paper and brush the bases with the remaining mixture. Leave to cool completely.
4. Meanwhile, for the filling, put the blueberries in a small pan with the lemon juice and sugar and cook for 2-3 minutes until softened but still holding their shape. Remove from the heat; tip into a sieve over a bowl, to collect the juice. Set the berries aside to cool.
5. To make the icing, use an electric hand whisk to beat the butter until smooth on its own (this is important or you will get lumps of butter). Beat in the cream cheese and icing sugar until smooth. Add the cream plus 1½ tablespoons of the cooled blueberry juice and whip until thick and just holding its shape.
6. Place a sponge flat-side down on a plate or board, spread with a thin layer of icing and the cooled berries. Place the second sponge on top. Cover the top and sides of the cake with the rest of the icing. Dip a pastry brush in the rest of the blueberry juice and flick over the cake (beware – it splashes everywhere!). Serve in slices; it will keep for 3-4 days in the fridge.