1. Roll out the pastry and line a flan tin.
2. Bake blind for 10 - 15 minutes at 200°C, 400°F, mark 6.
3. Peel the marrow, cut it in half and remove the seeds.
4. Cut the flesh into even-sized pieces and cook until soft in boiling, salted water (about 20 minutes). Drain well.
5. Peel, core, slice the apples, and stew them with the sugar.
6. Mix the stewed apple with the marrow, mash well, season, add the grated rind of the orange, sprinkle with lemon juice and dot with butter.
7. Put in the flan case and bake for 15 minutes at 220°C, 425°F, mark 7.