1. Preheat the oven to 170°C. Line a 23cm spring-form cake tin with baking paper and spray well with non-stick cooking spray. Fold a double layer of foil around the outside of the pan (this prevents any filling from leaking out or water from entering the cake tin while it’s in the water bath).
2. Whisk the egg whites until soft peaks form. Add the cream of tartar and whisk for another minute. Add the sugar a spoonful at a time until it forms a thick, glossy meringue.
3. Using a separate mixing bowl, beat the cream cheese, butter and milk until smooth. Add the egg yolks, lemon juice and vanilla and beat until smooth. Sift the flour, cornflour and salt over the mixture and beat until just smooth.