Soak the raisins in the rum and let them steep a little. Separate the eggs. Beat the egg whites with a little salt until stiff. Beat the butter until foamy, add the sugar and egg yolk. Stir in the ground poppy seeds, almonds, soaked raisins and the grated lemon zest. Finally, carefully fold in the stiffly beaten egg white.
Bake in a springform pan at around 180 degrees for around 60-70 minutes, depending on the oven. Make the icing from the remaining rum and powdered sugar. After cooling, turn the cake out and cover with icing if necessary.
After the frosting has dried, wrap it in aluminum foil and let it soak in the refrigerator for 2-3 days.