For the sheet cake with strawberries, cream butter with sugar, vanilla sugar, salt and grated lemon zest, add eggs gradually and then carefully fold in flour and baking powder.
Line a baking tray with baking parchment, spread the mixture about 2 cm thick and cover the tray with strawberries. Bake at 160°C (hot air) in a preheated oven for about 35-40 minutes.