Whisk the butter, sugar and salt in a bowl. Add the eggs one at a time and continue to whisk until the mixture becomes lighter in colour.
Mix the flour with all the other ingredients up to and including the ground cardamom, stir into the mixture along with the squash. Fill the prepared tin with the cake mixture.
Approx. 55 mins. in the centre of an oven preheated to 180°C. Remove the cake from the oven, allow to cool a little, remove from the tin and leave to cool on a rack. Dust with icing sugar.