01 - In a large bowl, mix flour and salt. Make a well in the center; add egg, vegetable oil, and lukewarm water. Combine ingredients and knead by hand for 8 to 10 minutes until smooth and elastic. Form into a ball, brush lightly with oil, cover, and let rest at room temperature for 30 minutes.
02 - In a separate bowl, gently toss sliced apples with raisins, granulated sugar, ground cinnamon, lemon zest, lemon juice, and nuts if using. Set filling aside.
03 - Melt 2 tablespoons of the butter in a skillet over medium heat. Add breadcrumbs and cook, stirring, for 2 to 3 minutes until golden brown. Remove from heat and allow to cool slightly.
04 - Set oven to 375°F. Line a baking sheet with parchment paper.
05 - On a lightly floured kitchen towel, roll rested dough into a rectangle about 24 by 16 inches. Using your hands, carefully stretch the dough until nearly transparent.
06 - Brush half the remaining melted butter over the surface of the stretched dough. Sprinkle toasted breadcrumbs evenly over dough, leaving a 2-inch border on all edges.
07 - Spread apple mixture evenly across the breadcrumb layer.
08 - Fold in the short edges of dough. Using the towel to assist, roll the strudel up tightly from the long edge to form a log. Carefully transfer seam-side down to the prepared baking sheet.
09 - Brush the exterior of the strudel with the remainder of the melted butter.
10 - Bake strudel for 35 to 40 minutes, or until golden brown and crisp.
11 - Allow strudel to cool slightly. Dust generously with powdered sugar, slice, and serve warm.