Grease the baking tray (approx. 35 x 40 cm). Wash the untreated lemon in hot water, dab dry and rub the peel. Squeeze the lemons and measure out 8 tbsp. juice. Cream butter, sugar, 1 vanillin sugar and lemon peel. Stir in eggs one by one. Mix flour and baking powder and stir in alternately with 4 tbsp. lemon juice in portions
Paint on the tin. Bake in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for approx. 20 minutes. Prick the hot cake several times with a wooden skewer. Mix 4 tbsp. lemon juice and icing sugar and sprinkle the cake immediately. Let it cool down
Place both bags of cake glaze in hot water for about 10 minutes. Spread the glaze on the cake. If necessary, pull through with a garnish comb and let dry
Cut the cake in half crosswise into 2 smaller plates. Whip the cream until stiff, while pouring in 1 vanilla sugar and cream firming agent. Spread on a cake plate, place the 2nd plate on top. Dust with cocoa