Preheat the oven to 320°F (160°C). Line the bottom and sides of an 8-inch round cake pan with parchment paper.
In a heatproof bowl, melt the cream cheese, butter, and milk over a double boiler. Stir until smooth, then remove from heat and let cool slightly.
Sift the cake flour, cornstarch, and salt into the cream cheese mixture. Stir until well combined. Add the egg yolks and mix until smooth.
In a separate bowl, beat the egg whites with lemon juice until frothy. Gradually add the sugar and continue beating until stiff peaks form.
Gently fold the whipped egg whites into the batter in three batches, being careful not to deflate the mixture.
Pour the batter into the prepared cake pan. Place the pan into a larger baking dish and fill the outer dish with hot water to create a water bath.
Bake for 60 minutes, then reduce the temperature to 300°F (150°C) and bake for another 10 minutes.
Turn off the oven and leave the cake inside with the door slightly open for 10-15 minutes. Allow it to cool completely before removing from the pan.