Preheat the oven to 180°C. Grease and line the base of a round cake tin.
Mix the cream cheese and yogurt until creamy a fluffy. Add the cornstarch, salt and Stevia, then combine. Gently stir in the egg and extra egg white, then add the lemon zest, juice and berries.
Tip the mixture into cake tin, spreading it out evenly.
Bake for 30 minutes, then allow to cool in the oven (with the door slightly open) for 20 minutes or so.
You can serve it lukewarm or let it cool completely, then refrigerate till serving.