Preheat the oven to 150°C. Greased and line the base of a cake tin.
Combine the almond flour, baking powder, bicarb and corn flour, then set aside.
In another bowl mix the butter, quark and Stevia.
Add the eggs, one by one, combine well then add the vanilla and lemon zest.
Stir in the dry mixture and combine.
Pour the batter into the cake tin.
Bake in the middle of the oven for about 50-60 minutes. If the top is getting too brown, cover it with foil.
Turn off the oven and open the door. Leave the cake to cool in the oven for 5 minutes, then take the tin out and let the cake cool in the tin for 15 minutes, then carefully remove it to a wire rack.
Serve it lukewarm or let it cool completely before serving.