Preheat the oven to 180C/Gas4; grease and base-line 2 x 18cm round pans and dust the sides with flour
Put the butter, sugar, lemon zest and juice, flour and eggs in a large bowl and beat with an electric hand beater until the mixture is pale and creamy
Spoon ¼ of the mixture into one pan and the same quantity into the other pan; level the surfaces and bake for 25 minutes or until just firm to the touch; remove from the pan and allow to cool
Wash the pans and grease and re-line; bake the remaining mixture in the same way and cool
Cut the centres of 2 of the cakes using a 9cm round shape; lift out the centres and keep for later use
To make the lemon butter icing put the butter, icing sugar and 1 tablespoon lemon juice in a large bowl and beat until smooth; add the rest of the lemon juice and beat again until pale and creamy
Place one of the whole cakes on a plate and spread the edges and top with a little lemon buttercream; position one of the ring cakes on top and spread the edges and top of this with the buttercream and position the second ring cake on top of it; tip the sweets into the cavity until it is completely filled
Spread the cake edges and top with more buttercream and position the remaining cake on top
Spread the remaining buttercream over the top and sides of the cake evenly
12 servings