The dough for Linzer Torte is a fragile, very buttery shortcrust, often with added cinnamon and cloves for a characteristic Christmas aroma. For the best result, use cold butter and do not overmix the dough to keep it crumbly. The dough must be thoroughly chilled before baking.
Tart redcurrant jam is traditionally used because its acidity contrasts nicely with the richness of the sweet nut dough. If redcurrant jam is unavailable, use raspberry or cranberry jam.
In a large bowl, mix flour, ground nuts, powdered sugar, cinnamon, and cloves. Add the diced cold butter and rub the mixture with your hands or a mixer until it resembles coarse crumbs.
Add the egg, egg yolk, and lemon zest. Quickly work into a smooth dough. Wrap the dough in plastic wrap and chill it in the refrigerator for at least 1 hour (ideally 2 hours).
Preheat the oven to 185 °C (365 °F). Prepare a tart pan (24–26 cm diameter) by greasing it with butter and dusting with flour.
Press two-thirds of the chilled dough into the pan and form an edge about 3 cm high. Prick the dough gently with a fork.
Brush the edge of the dough with the beaten egg and sprinkle with sliced almonds.
Spread the redcurrant jam evenly over the base.
Roll out the remaining third of the dough and cut it into strips (approx. 1 cm wide). Use the strips to form a lattice pattern on the surface of the jam. Brush the lattice with the beaten egg.
Bake in the preheated oven for 40–50 minutes, until the dough is golden brown and the jam is bubbling. If the lattice browns too quickly, cover it with aluminum foil.
Allow the cake to cool completely in the pan. Linzer Torte tastes best on the second or third day, once the flavours have developed and the jam has moistened the dough. Dust with powdered sugar before serving.