(click on the text to highlight each stage):
- Heat the oven to 170°C, 325°F, gas 3. Grease a large loaf tin.
- Beat the butter, half the sugar, nutmeg and salt in a mixing bowl until creamy. Split the vanilla pod and scrape out the seeds into the mixture.
- Beat in the egg yolks one at a time until the mixture is smooth.
- Whisk the egg whites with the remaining sugar until stiff.
- Stir together the ground almonds, flour, potato flour, baking powder and cranberries in a bowl. Add half the mixture to the mixing bowl and stir well.
- Whisk the egg whites until stiff but not dry and fold into the mixutre until incorporated. Gently stir in the remaining flour mixture.
- Spoon into the loaf tin and bake for 45-55 minutes until risen and golden. Insert a skewer into the centre of the cake, which should come out clean.
- Cool in the tin for 10 minutes, then turn out onto a wire rack to cool.
- For the icing: sift the icing sugar into a bowl and stir in the cranberry juice and a little colouring if liked. Spread the icing on top of the cake and leave to set.