Using the whisk on a hand mixer, beat the sugar, egg yolks and oil in a bowl for approx. 3 mins. until light and fluffy. Add the parsnips, cinnamon, cardamom and tangerine zest, mix in. Combine the hazelnuts, pecan nuts, flour and baking powder, stir into the mixture. Beat the egg whites with the salt until stiff, carefully fold into the mixture using a rubber spatula. Transfer the sponge mixture to the prepared tin.
Approx. 50 mins. in the lower half of an oven preheated to 180°C. Remove from the oven, allow to cool slightly, remove from the tin and leave to cool on a rack.
Beat together the butter and icing sugar using the whisk on a hand mixer until the mixture becomes lighter in colour. Add the cream cheese and reserved tangerine juice, mix well. Spread the frosting on top of the cake, decorate with pecan nuts and tangerine zest.