Sift the flour onto the surface, make a dent in the center and pour in the egg, salt and oil. Knead carefully, gradually adding the water. Work vigorously with your hands to form a medium-firm, smooth dough. Form a ball, brush with oil and rest for half an hour.
In the meantime, remove the skin from the apples, remove the core and finely slice. Mix them in a baking bowl with the sugar, the cinnamon powder, the grated lemon peel, the raisins, the pine nuts and the rum. Leave to rest for a few minutes.
Melt the butter and toast the bread crumbs in it. Flour a clean kitchen towel and roll out the dough on it. Gently pull the dough with your hands until it is very thin. Be careful not to tear the dough.
Brush the dough with the melted butter, sprinkle bread crumbs on 2/3 of the dough surface and spread the apples evenly on top. Lift the kitchen towel on the side with the filling and roll it up leisurely and carefully. Place the strudel on a greased baking tray, brush with the remaining butter and bake in a heated oven at 220 °C for about half an hour.
Sprinkle with powdered sugar before serving.
Apple strudel tastes best lukewarm and with whipped cream.