Laminated dough
Knead wheat flour with sunflower oil, salt and water in the food processor with the flex edge beater for about 5 minutes until the dough is no longer sticky. Shape the dough into a ball and place in a bowl. Brush the surface with sunflower oil and cover with cling film. Let rest at room temperature for about 1 hour.
Roll out the dough very thinly on a clean kitchen towel with a little flour. Reach under the dough with both hands and pull the dough apart (very thinly) so that you can almost see through it. (Please note: Pull carefully so that the dough does not tear!).

Crumbs
Melt the butter in a pan, brown the sponge cake crumbs and let cool (If you use breadcrumbs instead of sponge cake crumbs, you have to add sugar, cinnamon and lemon.

Filling
Wash, peel and halve the apples, remove the core and cut into very thin wedges. Place the apple slices in a bowl. Coarsely chop the walnuts or pine nuts and add them to the apples together with raisins, rum, cinnamon, vanilla, lemon zest and juice. (If you want, you can soak the raisins in the rum overnight.) Add sugar and crumbs to taste. (If you use breadcrumbs, you need a little more sugar than for sponge cake crumbs.) Mix well.

Completion
Brush the dough with melted butter and sprinkle with some of the crumbs. Distribute the filling over a little more than a third of the dough, fold the outer sides of the dough inwards so that the filling cannot fall out. Carefully lift and roll up the strudel with the help of the kitchen towel. Twist in the ends and place them under the strudel.

Place the strudel on a baking tray lined with baking paper and brush again with melted butter. Bake in the oven for 28 minutes at 175°C (convection oven). Remove the strudel from the oven, let cool and sprinkle with powdered sugar.