Step 1:Preheat the oven to 170°C (fan 150°C, gas mark 3) and grease an 28cm (11in) springform cake tin. Step 2:Cream 180g (6½oz) of the sugar, zests and egg yolks together until light and fluffy. Next, stir in the ground almonds, almond extract and the cinnamon.Step 3:In a separate bowl, beat the eggs whites with the remaining sugar until stiff. Add about one-quarter of the egg whites into the thick almond mixture and beat. Add a further quarter and repeat. Add the remaining egg white mixture and fold in until fully combined.Step 4:Turn the mixture into the prepared tin and bake in a preheated oven for 40 minutes.Step 5:Remove from the oven, allow to cool for 10 minutes in the tin and then turn out onto a wire rack.Step 6:To follow the time-honoured tradition of decoration, find the shape of the St James cross using the internet and print it out. Cut out the middle of the cross to use as a stencil.Step 7:Once the cake is cooled, dust the cake with icing sugar and serve straightaway