01 - Preheat oven to 320°F. Line bottom and sides of 8-inch round cake pan with parchment paper. Wrap exterior with foil to create water-tight seal.
02 - Set heatproof bowl over pot of simmering water. Melt cream cheese, butter, and milk, stirring until smooth. Remove from heat and cool slightly.
03 - Sift cake flour, cornstarch, and salt into dairy mixture. Whisk until completely smooth and no lumps remain.
04 - Mix egg yolks, lemon juice, vanilla extract, and lemon zest into batter until fully combined. Set aside.
05 - Beat egg whites with electric mixer until foamy. Gradually add 5 tbsp sugar in three batches, beating until stiff glossy peaks form.
06 - Gently fold one-third of meringue into batter to lighten. Fold in remaining meringue in two additions, maintaining air structure.
07 - Pour batter into prepared pan. Tap pan firmly on counter several times to release trapped air bubbles.
08 - Place cake pan in larger roasting pan. Pour hot water into roasting pan until halfway up cake pan sides.
09 - Bake for 60-70 minutes until golden brown, set, and skewer inserted in center comes out clean.
10 - Turn off oven, leave door slightly ajar, and let cake rest inside for 15 minutes to prevent cracking.
11 - Remove from oven, cool completely in pan. Refrigerate at least 2 hours before unmolding and serving.