Knead the spelled flour, sugar, pieces of butter, eggs and salt quickly into a shortcrust pastry.
Press the dough flat in a buttered pie, spring or quiche tin (approx. 28 cm), forming a border of approx. 2 cm. Score or quarter the halved plums at the top and bottom and lay out on the dough in a fan shape.
Beat the cold cream vigorously with a mixer or whisk (it should still be thick), whisk the cinnamon sugar and egg well in it and distribute the mixture on the fruit.
Bake at about 180 ° for about 45 minutes.
The flan can be eaten warm, but the icing is still a little runny.