Place the butter in a bowl, whisk in the sugar and salt. Add the eggs one at a time and continue to whisk until the mixture becomes lighter in colour. Stir in the orange zest. Combine the flour and baking powder, stir into the mixture. Transfer the cake mixture to the prepared tin.
Approx. 45 mins. on the bottom shelf of an oven preheated to 180°C.
Remove the cake from the oven, allow to cool slightly, prick firmly all over with a wooden skewer.
Combine the orange juice and icing sugar, pour over the cake. Remove the cake from the tin, leave to cool on a rack.