Grease a springform pan (26 cm Ø) and sprinkle with hazelnut leaves. Wash, halve and stone the plums. Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer).
For the dough, separate 3 eggs and chill the egg whites in a mixing bowl. Cream 125 g butter, 100 g sugar, vanilla sugar and 1 pinch of salt with the whisks of the mixer. Stir in the remaining egg and egg yolk one after the other.
Mix flour, starch and baking powder. Alternately stir cream into the butter-egg-cream and spread it in the form. Add plums. Bake in a hot oven for 40-45 minutes.
For the meringue topping, beat the cold egg whites and lemon juice until stiff about 10 minutes before the end of the baking time, adding 150 g sugar. Continue beating for about 2 minutes until the mixture is shiny.
Take out the cake, spread the egg white mixture loosely on top. Bake at the same temperature for 5-8 minutes. Take the cake out of the oven, carefully remove from the edge of the pan with a knife. Let it cool down.