Preheat the oven to 170°C/Fan 150°C/Gas 3. Grease and base line an 18cm round cake tin.
Whisk the butter, sugar and vanilla extract until pale and fluffy. Whisk in the eggs, one at a time, until combined (add a little of the flour if it looks curdled). Mix in the red food colour. Fold in the flour and cocoa.
Spoon into the cake tin and bake for 50 minutes to 1 hour or until a skewer comes out clean when inserted into the cake. Allow to cool.
To make the filling, whisk the butter, vanilla extract and sugar until pale and fluffy
Cut the cake into 3 even-sized horizontal rounds. Spread ⅓ of the butter icing over 1 slice of cake, and then lay another slice on top. Spread this with another ⅓ of the icing and top with final slice. Spread with the remaining icing and sprinkle over the dried raspberries.