1 Preheat the oven to 160°C convection (approximately 320°F). Butter the springform pan and sprinkle with breadcrumbs.
2 For the dough: Peel the lemon and squeeze the juice. Mix the flour with the cornstarch and baking powder in a bowl. Melt the butter in a small saucepan.
3 Break the eggs into a mixing bowl and beat with an electric mixer until fluffy. Add in the lemon juice and zest. Alternately add in the melted butter and the flour mixture into the custard until a supple, smooth dough is formed. Pour the batter into the pan and bake until golden brown, about 50 minutes. Check doneness with a toothpick.
4 Remove from oven and allow to cool in the pan.
5 For the filling: Wash the plums, halve, remove the pit and slice into fine columns. Reserve a few columns for garnishing. Slice the vanilla pod open and boil with the brandy and the jam sugar for about 4 minutes while stirring. Remove from the heat and let cool, then remove the vanilla pod.
6 Soften the gelatine in cold water. Mix the yogurt with the sugar. Melt the gelatin into 2 tablesppons of heavy cream in a small saucepan. Stir in the yogurt. Whip the cream until stiff and fold it in.
7 Cut the cake horizontally and spread about 2/3 of the plums and the cream between the two layers. Brush the top with remaining plums.
8 Knead the marzipan with the powdered sugar and roll out to 2-3 mm thin (approximately 1/10 inch). Roll into a circle slightly larger than the cake cut and set with the help of the rolling pin over the cake. Press around and smooth it out. Cut the excess edges and knead together these excess pieces to form decorations. Serve decorated with the remaining plums.