For the sponge mixture, grease a springform pan (26 cm Ø) and dust with flour. Wash plums, remove stalks, halve and stone them. Separate 3 eggs. Cream butter, 100 g sugar, vanilla sugar and 1 pinch of salt.
Stir in 1 egg and 3 egg yolks separately. Mix flour, starch and baking powder and stir into the dough alternating with the cream. Fold in grated coconut. Spread the dough into the springform pan. Spread plums on the dough.
Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer) for approx. 45 minutes.
For the meringue topping, beat 3 egg whites and lemon juice until stiff, adding 150 g sugar. Continue beating until the sugar is completely dissolved.
Take the cake out of the oven and spread the beaten egg white loosely on top. Continue baking at the same temperature for 5-8 minutes. Remove from the edge of the springform pan and let it cool down in the pan.