Zest two oranges with the zester blade. Combine the orange peel, sugar, flour, butter, salt and all spices in a medium size bowl. Mix all together with a food processor or fork until a homogeneous mass of dough has formed. Spoon half the mixture into a buttered cake pan.
Stir baking soda into sour cream and mix all into the remaining dough mixture. Add eggs and combine thoroughly. Put the remaining dough into the pan and sprinkle top with chopped nuts.
Bake in 175°C oven for 40-45 minutes.
Whip cream until stiff using an electric mixer. Stir in sugar, orange peel and liqueur. Let stand in refrigerator for about one hour to combine flavors.
Cake is best served warm topped with orange whipped cream.