1. Cream butter and sugar until light and fluffy, add egg yolks and beat in well.
2. Sift flour, baking powder, cinnamon and salt twice.
3. Beat egg whites until stiff.
4. Fold sifted flour into creamed mixure, then mix in about a third of the beaten egg whites.
5. Fold in ground walnuts and lastly fold in remaining egg whites, using a metal spoon to blend mixture evenly and quickly.
6. Spread evenly into a buttered 23 * 30 cm (9 * 12 inch) baking dish and bake in a moderate oven for 45 minutes or until cake is cooked when tested.
7. Meanwhile dissolve sugar in water over heat; add cinnamon bark and lemon juice and bring to the boil. Boil for 10 minutes; remove from heat; stir in brandy; cool; and strain into a jug.
8. Pour cold syrup evenly over hot cake and leave cake until cool. Cut into squares or diamond-shaped pieces to serve. Delicious served with whipped; unsweetened cream.