For the walnut cake, first prepare the shortcrust pastry. Quickly knead flour, sugar, butter, egg and salt into a smooth shortcrust pastry. Form a ball, wrap in plastic wrap and let rest in the kitchen cupboard for about 1 hour.
Roughly chop the nuts, setting aside a few walnut halves for garnish.
Melt butter with sugar in a saucepan and let caramelize, stirring constantly. When the caramel starts to darken, deglaze with the orange juice, continue stirring to dissolve any lumps.
Stir in honey, cream, cinnamon and orange zest and bring to a boil. Stir in the chopped nuts, remove the pan from the heat and allow the mixture to cool.
Grease a springform pan (ø approx. 24 cm). Roll out about two-thirds of the short pastry and line the bottom of the cake tin with it. Raise a rim. Now spread the cooled nut mixture on top.
Roll out the remaining short pastry and cut into strips with a knife. Place the strips on the cake in a lattice shape and brush the pastry lattice with egg yolk.
Bake the cake in the preheated oven at 200 °C for 35-40 minutes. Garnish the walnut cake with the walnut halves.