Preheat Oven: Set oven to 320°F (160°C). Line a 12-cup muffin tin with cupcake liners or grease them lightly.

Cream Cheese Mixture: In a saucepan, melt cream cheese, butter, and milk over low heat. Stir until smooth. Let cool. Whisk in lemon juice and vanilla.

Dry Ingredients: In a bowl, whisk flour, cornstarch, and salt. Set aside.

Yolk Mixture: In another bowl, whisk egg yolks with sugar until pale. Gradually whisk in cooled cream cheese mixture.

Combine with Dry: Sift in the flour mixture and stir until smooth.

Whip Egg Whites: In a clean bowl, beat egg whites to soft peaks. Gradually add remaining sugar and beat to stiff peaks.

Fold: Gently fold egg whites into the batter in thirds to maintain airiness.

Bake: Fill cupcake liners ¾ full. Tap the tray to release air bubbles. Bake for 20–25 minutes until golden and a toothpick comes out clean.

Cool & Serve: Let cupcakes cool in the tin for 5 minutes, then transfer to a wire rack. Dust with powdered sugar if desired. Best served room temperature or chilled.