Grease a box form (approx. 1 3⁄4 l capacity; 30 cm long) and dust with flour. Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). For the dough, rinse lemon hot, dab dry and finely grate the peel.
Mix 250 g butter, 200 g sugar and 1 pinch of salt with the whisk of the mixer for about 5 minutes until light creamy. Stir in the eggs one after the other. Mix 150 g flour, starch, baking powder and semolina. Stir briefly into the butter and egg yolk cream.
Smooth the dough in the form. Bake in a hot oven for 50-60 minutes. Let the cake cool down. While still lukewarm, carefully turn out onto a cake rack and let it cool down.
For the filling, whip the sour cream with the whisks of the mixer until creamy. First stir the vanilla cream until smooth, then stir into the sour cream. Stir fruit jelly until smooth.
Cut the lemon cake into slices just under 1 cm thick. Spread half of the slices with approx. 1 tsp. jelly each. Spread the rest of the slices each with approx. 1 tbsp. vanilla cream and combine with the jelly cake slices.