This is easy to make and tastes delicious...don't think it'll be around too long!
6oz/175g caster sugar
6oz/175g butter, softened
3 eggs
8oz/225g self-raising flour
1 orange
1 lemon
6oz/175g icing sugar
Cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time with a little of the flour. Add most of the zest from the orange and lemon (retain a little for the icing).
Grease and line the bottom of a 9in/23cm square tin. Spread the mixture in the tin and bake at 150C, gas mark 2 for about 30 minutes. Leave to cool.
Make the icing by mixing the icing sugar with the juice from half the orange and lemon. Spread the topping over the cake and sprinkle the remainder of the zest on top. Cut into squares.
GilraenH
Pro 
Oh, this sounds lovely - will try this next week, I have some visitors coming that will appreciate it!