For the meringue berry tart with cream filling, first preheat the oven to 180 °C top/bottom heat.
Separate the eggs for the sponge cake. Beat the yolks in a large bowl with the icing sugar, vanilla sugar, lemon zest and salt using a mixer or food processor until very foamy. Beat egg whites in a second bowl until very firm. Sift flour onto a piece of baking paper and gently fold into the yolk mixture, alternating with the beaten egg whites, using a whisk.
Line a springform pan or cake ring with a diameter of approx. 24 cm with a piece of baking paper, spread the mixture in it and smooth it out. Bake in the preheated oven for about 15 minutes. Remove from the oven, let cool and remove from the pan. Then cut into 3 equally thick bases with a bread knife or thin thread and spread apart to cool.
Soak gelatin in about 500 ml cold water for 10 minutes, squeeze out and melt briefly in a cup in the oven.
Wash the berries if necessary, remove the green from the strawberries. Set aside a few at a time for decoration. Puree the remaining berries according to type and pass through a fine sieve.
Whip the cream until stiff. Mix curd with powdered sugar, lemon juice and zest and stir in melted gelatine. Divide curd mixture into thirds and mix each with one of the 3 berry purees. Divide whipped cream among the 3 creams and fold in.
Place a piece of cake base in a cake ring and spread a thin layer of jam on top.