For the dough, mix 1½ cups of all-purpose flour, 1 pinch of salt, 1 medium egg, 1 tablespoon of vegetable oil, and 6 tablespoons of lukewarm water. Knead for about 5 minutes.
Shape into a ball, coat with 1 teaspoon of vegetable oil, and leave under a kitchen towel for 30 minutes.
Meanwhile, melt 3 tablespoons of butter in a frying pan and toast ⅓ cup of plain breadcrumbs in it until browned.
Mix 4 peeled and chopped Granny Smith apples with ¼ cup of sugar, 1 teaspoon of ground cinnamon, 2 tablespoons of lemon juice, 2 tablespoons of rum, ⅓ cup of raisins, and the breadcrumbs.
Preheat the oven to 400°F / 200°C and line a baking sheet with parchment paper. On a floured kitchen towel, stretch the dough into a thin 24 × 17in / 61 × 43cm rectangle.
Brush with 1 tablespoon of melted butter and spread the filling over it, leaving a 2in / 5cm border. Roll it up with the help of the towel and set it seam side down on the baking sheet.
Bake on the middle rack for 30-40 minutes, brushing with a little more melted butter after 15 minutes, until lightly browned. Cool for a few minutes, then dust with icing sugar.
