Preheat your oven to 320°F (160°C). Grease an 8-inch (20cm) round cake pan with butter and line the bottom and sides with parchment paper. Grease the parchment as well.

In a double boiler, melt the cream cheese, butter, milk, and 1/4 cup (50g) of sugar together until smooth.

Remove from heat and stir in the egg yolks until thoroughly combined. Sift in the flour and cornstarch, then add the lemon zest and juice.

Whisk the egg whites at low speed until foamy. Gradually add the remaining sugar while beating until stiff peaks form.

Fold one-third of the egg whites into the cream cheese mixture, then gently fold in the remaining egg whites in two additions.

Pour the batter into the prepared pan and tap on the counter to release air bubbles.

Place the cake pan into a large roasting pan. Pour boiling water into the roasting pan until it reaches halfway up the sides of the cake pan.

Bake for 20 minutes, then reduce the temperature to 285°F (140°C) and bake for an additional 30-35 minutes.

Turn off the oven and let the cheesecake cool in the oven for 30 minutes.

Remove from the oven and let cool completely before serving.