For the shortbread base, knead 350 g flour, 100 g sugar, egg and 250 g butter in pieces, first with the dough hooks of the mixer, then briefly with your hands to form the smooth dough. Cover and chill for about 30 minutes.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Grease a square springform pan (24 x 24 cm; alternatively round, 26 cm Ø) and dust with flour. Press the dough in the form to a base, prick several times with a fork.
Bake in a hot oven for about 20 minutes until golden brown.
For the baked apple filling, meanwhile, wash the lemon hot, dab dry and finely grate the peel. Squeeze the lemon. Peel, quarter and core the apples. Mix with 2 tbsp. sugar, lemon peel and juice in an ovenproof dish.
Take the shortbread base out of the oven and let it cool down. Turn up the oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Stew apples in it for about 20 minutes until soft.
For the toffee filling, boil 250 g butter, syrup and cream. Boil down at medium heat for approx. 25 minutes while stirring constantly until creamy. Roast the almonds in a pan without fat, turning constantly, until golden brown, take them out and let them cool down.
Spread the baked apples on the shortbread base. Add hot toffee mixture, up to approx. 4 tbsp, and let cool. Stir the almonds into the remaining warm toffee mixture. Pour onto baking paper and allow to cool.
Chill the cake and toffee almonds for about 1 hour.
For the crème fraîche and 3 tablespoons of sugar, whisk with the whisks of the mixer for about 1 minute. Spread on the cake. Cut the toffee almonds into pieces and sprinkle over them. Carefully remove the cake from the tin.
Cut into about 20 pieces.