Wash lemon hot, rub dry and cut off 1 lemon spiral. Separate the eggs. Boil milk, sugar, lemon peel and salt in a pot while stirring. Sprinkle in semolina while stirring and boil up briefly while stirring.
Pull the pot off the stove. Mix the egg yolks and 1-2 tablespoons of hot semolina. Then stir into the remaining semolina. Let the semolina swell for 5-10 minutes. Remove lemon peel. Beat the egg whites until stiff and fold loosely into the semolina.
Drain the plums and collect the juice. Stir 4 tablespoons of juice and starch until smooth. Boil up the rest of the juice, vanilla sugar and cinnamon. Stir the starch into the boiling juice and simmer for 2-3 minutes.
Fold in plums. Serve semolina with compote warm or cold.