Preheat your oven to 350 degrees Fahrenheit (177 degrees Celsius).
Grease a 9-inch cake pan and line the bottom with parchment paper.
In a pot on the stove, melt the cream cheese, butter, and milk, and whisk together until smooth, then remove from the heat and set aside.
Separate the egg yolks and egg whites into two large bowls. Once the cream cheese mixture has cooled to room temperature, whisk it into the bowl with the egg yolks.
Next, add the lemon juice, vanilla, and half of the sugar into the mix.
Then, add the flour, cornstarch, and salt into the mix and whisk together until there are no more lumps.
Next, in the bowl of egg whites, use a hand mixer and whip the egg whites. Once soft peaks are reached, add in the sugar and cream of tartar and continue mixing until firm peaks are formed.
Then, and this is the most important step, using a metal spoon, gently fold in ⅓ of the egg whites into the mixture and then fold in the remainder of the egg whites ever so lightly into the mix.Note: The batter should look almost marbled, do not fully incorporate them together or it won't come out correctly, and you will lose the bubbles and air in the batter.
Pour the batter into the cake pan place the cake pan on a baking sheet with sides, and add in a very thin water bath using hot water (if it’s easier to add the water when it’s already in the oven, that works too and keeps water off your floors).
Bake at 350 degrees Fahrenheit (177 degrees Celsius) for 30 minutes, then lower the temperature to 300 degrees Fahrenheit (149 degrees Celsius) and bake for 12 minutes. After this, turn the oven off and open the oven door slightly for 30 minutes, then remove from the oven and the water bath and allow the cake to cool to room temperature.
Finally, top with a generous dusting of powdered sugar, and enjoy!
Video
Notes
You can store this dish in an airtight container on your countertop for 2-3 days. You can also store this cake in your fridge in an airtight container for 3-5 days.If you want to freeze this cake, you can do so for up to 2 weeks in your freezer in an airtight container, but note that you will lose some of the fluffy consistency by doing this. I would not recommend freezing this dish.