Line a springform pan (Ø 24 cm) with baking paper. Preheat the oven (top / bottom heat: 180 ° degrees / convection: 160 ° degrees). Wash the organic lemon with hot water, dry it and finely rub the peel. Wash the plums, pat dry, stone and quarter.
Put the milk, sugar and vanilla sugar in a saucepan and bring to the boil. Stir in the semolina with the whisk. Take the pan off the stove and let the semolina swell for about 3 minutes. Separate the eggs. Beat the egg whites until stiff. Stir egg yolks, butter, lemon zest and almonds into the semolina while it is still hot.
First fold the egg whites and then the plums into the semolina mixture. Pour the mixture into the prepared springform pan and bake for about 50 minutes. Take the cake out of the oven and let it cool in the tin for about 20-30 minutes. Then carefully loosen the edge of the mold and put in the cold. Sprinkle with powdered sugar before serving.