Sift the sugars into a large bowl and mix with the ground almonds.
Grate in the orange zest then mix to a firm dough with the beaten eggs and some of the orange or lemon juice.
Knead the dough lightly until it is smooth and soft.
Cover the cake with almond paste a good two or three days before icing it.
Beat the egg whites in a large bowl until frothy.
Beat half the sifted icing sugar and all of the lemon juice into the egg whites.
Stir in the remaining icing sugar until you have a thick paste.
Cover with a clean, wet towel until needed.
Brush the top of the cake with sieved apricot jam.
Roll out the almond paste and cover the top and sides of the cake.
Cover loosely with tin foil and lift into a cake tin where it should sit for a day or two before icing.
