Mix flour, corn starch & baking powder. Set aside.
Finely grate the zest of the lemon.
W/ the electric handheld mixer whip the sugar & the butter. Add the egg yolks, the lemon zest, the lemon juice & the vanilla extract & mix until creamy.
Add the flour mix & whip.
Add the low-fat curd cheese & whip.
Whip the egg whites w/ a pinch of salt until firm & fold it into the mess.
Pour everything in the spring form & let it bake in the oven for about 45 min.
After the oven session let it cool for about 10 - 15 min before removing the frame. Try to peel off the baking pachment very carefully.
Let it cool down completely before sliding the cake on a plate & removing the rest of the baking parchment. (Trust me it'll work when carefully detauching the bottom of the cake at first & then pull also carefully at the baking parchment.)
Put the frozen red berries in a pot & bring it to a boil.
Add sugar & stir until dissolved.
Add corn starch for thickening if you like.
Let the mess cool down before serving (chill in the fridge).
Notes
The cake will be fine for 3 - 4 days in the fridge.