Place raisins in a small bowl and soak them in a cup of warm water mixed with rum (optional). While the raisins soak, prepare the apples.

Wash and peal the apples.

Slice the apples into very thin slices.

Place the sliced apples in the sieve. Sprinkle them with lemon juice to avoid browning and let them rest for about 10 - 15 minutes. Gently stir the apples to allow the extra juice to drain.

Transfer the apples to a large mixing bowl and add the brown sugar, cinnamon, and raisins, and gently stir with a spoon.

The filling is ready to be added to the dough to make the apple strudel.