Preheat oven to 350F (180C). Soak the raisins in warn water or in rum for 20 minutes.
Make the filling: in a medium size pan, melt the butter over low-medium heat. Add the breadcrumbs and toast for 2-3 minutes. Remove and set aside.
In a large bowl, mix diced apples, lemon juice, lemon zest, sugar, cinnamon, salt, drained raisins, chopped walnuts.
Lay a thin kitchen towel on the counter. Place 1 sheet of phyllo dough on the towel. Brush the phyllo with melted butter, then Layer with 7 additional phyllo sheets, brushing each layer with some of the butter mixture.
Brush the last layer with melted butter and sprinkle the breadcrumb mixture, spread the apples over the breadcrumbs on the long side, leaving 2-inches (5cm) on the edges.
Fold the short edges over the filling, then, roll the strudel. Gently transfer to a baking tray. Brush the top of the strudel with melted butter.
Bake for about 40-45 minutes, or until golden brown.
Allow to cool slightly. Dust with powdered sugar before serving.