Bring lemonade to the boil in a saucepan and boil down to approx. 120 ml for about 10 minutes. Let cool down. Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Grease an ovenproof pudding mould or narrow, tall ring cake mould (approx. 2 l capacity) and dust with flour.
Cream 200 g butter and 250 g sugar with the whisks of the mixer. Stir in the eggs one after the other. Mix 300 g flour and baking powder. Stir 100 ml lemonade into the butter-sugar-cream.
Smooth the dough in the tin and bake in a hot oven for approx. 1 hour (chopstick test). Take out, let rest for about 15 minutes. Carefully turn out of the tin onto a cake rack. Let it cool down.
Stir icing sugar and 2 tablespoons of lemonade to a smooth glaze. Cover the cake with the icing so that the icing runs down slightly nasty. Let the icing dry. Whip the cream until stiff, adding 2 tbsp. sugar.
Fold in sour cream. Turn the cake over. Spread the cream on the cake. Sprinkle with glitter sugar.