Melt the butter and let it cool down a bit. Flour, egg yolk, sugar, citrus. Process the bowl with butter into a crumbly dough and press half of it onto the greased base of a springform pan.
Prepare pudding with milk and let cool down a little. Beat egg whites until stiff, fold in pudding and nut filling. Then gently stir in the cherries and egg whites and spread them on the cake base, pour the remaining crumble on top.
Bake at 180 ° for approx. 1 hour (after approx. 1/2 hour cover with aluminum foil) - needle test.
When cold, sprinkle with icing sugar or pour lemon glaze over it.