Preheat oven to 320°F (160°C). Line a muffin tin with paper liners. Prepare a hot water bath or place a pan of water on the bottom rack.

In a double boiler over simmering water, melt cream cheese, butter, and milk. Whisk until smooth. Remove from heat.

Whisk in egg yolks, vanilla, and lemon juice into the cheese mixture.

Sift cake flour and cornstarch into the wet mixture. Whisk gently until smooth, then strain through a sieve to remove lumps.

In a separate clean bowl, whip egg whites until foamy. Gradually add sugar and whip to soft peaks (peaks that droop slightly).

Fold 1/3 of the meringue into the cheese batter to lighten it. Gently fold in the remaining meringue in two batches without deflating the air.

Pour batter into muffin liners, filling about 80% full. Tap the tin on the counter to release large bubbles.

Bake for 40-50 minutes until golden brown and puffed.

Turn off oven and leave door ajar for 10 minutes, then remove cupcakes to cool on a wire rack. Dust with powdered sugar.