Preheat the oven to 325 degrees.
Melt the cream cheese, butter, and milk in a saucepan over medium-low heat, stirring often.
Once melted, pour in a bowl and fold in the flour, cornstarch, egg yolks, salt and lemon juice. If your mixture gets too warm, be sure to temper the egg yolks.
In a separate bowl, whip the egg whites until frothy.
Add the cream of tartar.
Add the sugar, a little at a time, while continuing to whip the egg whites until soft peaks form.
Fold 1/3 of the egg white mixture into the cream cheese mixture. Then fold the next 1/3 in, and the last 1/3 in in separate batches, being careful not to over mix.
DO NOT OVER MIX. Make sure you fold the egg whites into the cream cheese mixture gently. Otherwise your cheesecake will deflate when baking.
Pour mixture into a well greased 8 or 9" spring form pan.
Wrap aluminum foil around the bottom 1.5" of the pan. Set it a water bath to cook to avoid cracking on top. If you don't care about cracking, you can skip this step.
Bake for 60-70 minutes, or until a toothpick comes out clean.
Remove from heat and let cool for 1 hour. Remove from spring form pan and refrigerate overnight.
Serve with a dusting of powdered sugar and/or fresh berries.