Begin by preheating your oven to 320°F (160°C). Line a 12-cup muffin tin with cupcake liners.

In a medium saucepan, combine the cream cheese, unsalted butter, and whole milk. Stir continuously over low heat until smoothly blended, about 5-7 minutes. Let it cool to room temperature.

In a mixing bowl, whisk together all-purpose flour, cornstarch, and salt until well combined.

In a large bowl, whisk egg yolks with granulated sugar and lemon juice until pale and thick, about 3-5 minutes. Mix in the cooled cheese mixture.

Sift the dry ingredient mixture into the yolk mixture in increments and gently stir until fully incorporated.

In a separate bowl, beat egg whites on medium speed until soft peaks form. Gradually add remaining sugar until stiff peaks form, about 3-5 minutes.

Fold one-third of the whipped egg whites into the batter, then fold in the remaining egg whites until well incorporated.

Pour the batter into the lined muffin cups, filling each about three-quarters full. Bake for 20-25 minutes until golden.

Let the cupcakes cool in the pan for about 5 minutes, then transfer to a wire rack to cool completely. Dust with powdered sugar before serving if desired.