Defrost the berries for the spring cake. Grease a springform pan (26 cm Ø) and dust with flour. Stir 150 g butter, 175 g sugar, 1 pinch of salt, lemon peel and lemon juice until creamy. Stir in the eggs one by one. Mix 150 g flour, starch and baking powder, stir in. Spread into the form. Bake in the preheated oven (electric oven:175 °C/ convection oven: 150 °C/gas: level 2) for about 25 minutes. Cool down.
Soak the gelatine in cold water. Pass berries through a sieve and mix with 125 g sugar. Squeeze the gelatine and dissolve at low heat. Stir in 2 tbsp. raspberry puree, then stir into the rest of the puree. Chill for about 5 minutes until it starts to gel.
Cut the cake base in half horizontally. Close the cake ring around the lower cake base. Whip 500 g cream until stiff. Fold into the purée. Spread on the lower cake base. Place 2nd cake base on top. Chill for about 4 hours.
Whip 800 g cream until stiff, pouring in cream firming agent and vanillin sugar. Spread a thin layer of cream on the cake. Pour the rest of the cream in portions into a piping bag (large star-shaped spout). Spray rosettes on the whole spring cake and decorate with sugar flowers etc.