Prepare an 8-inch round cake pan by lightly greasing and lining the bottom and sides of it with greaseproof baking paper or parchment paper. Note: You don't want to use a springform pan unless it is water tight because this cake is baked in a water bath.
Melt cream cheese, butter and milk over a double boiler.
Cool the mixture.
Fold in the flour, cornstarch, egg yolks, lemon juice and mix well.
Whisk egg whites with cream of tartar until foamy.
Add the sugar into the egg white mixture and whisk until soft peaks form.
Add the egg white mixture to the cheese mixture.
Carefully fold until well blended! Do not overmix or the cheesecake will be dense and heavy.
Pour mixture into prepared pan.
Bake cheesecake in a water bath for 1 hour and 10 minutes, or until set and golden brown.