Grind walnuts for the short pastry. Mix flour with sugar and walnuts. Add butter in pieces and water and chop through everything with a knife to form dry crumbs. Then knead everything by hand to a smooth dough.
Roll out the dough on a floured work surface and line a tart or pie dish (28-30 cm diameter) with it, pressing the rim up. Prick the dough several times with a fork. Place the mould in the refrigerator for 1 hour.
Quarter the pears, remove the seeds and peel them. Cut pears into slices and place them on the dough. Sprinkle sugar over them. Bake in a preheated oven at 200-220 degrees (gas: level 4-5, fan oven: 180-200 degrees) for about 25 minutes.
Chop the walnuts and sprinkle them together with the cranberries on the tart for the last 5 minutes.