2. Melt the cream cheese mixture:
In a heatproof bowl over a double boiler, melt cream cheese, butter, and heavy cream. Stir until smooth.
Remove from heat and let cool slightly.
3. Mix the batter:
Whisk in egg yolks, granulated sugar, lemon zest, sifted flour, and cornstarch until smooth.
4. Prepare the meringue:
In a clean bowl, beat egg whites with cream of tartar until foamy.
Gradually add granulated sugar and beat until stiff peaks form.
5. Combine batter and meringue:
Gently fold the meringue into the batter in 3 additions, using a spatula to keep the mixture airy.
6. Bake using a water bath:
Pour the batter into the prepared cake pan.
Place the pan in a larger baking dish and fill with hot water (about 1 inch deep).
Bake for 60-70 minutes or until the top is golden brown and a toothpick inserted comes out clean.
7. Cool and serve:
Let the cake cool in the oven with the door slightly open for 10-15 minutes to prevent shrinking.
Remove from the pan, dust with powdered sugar if desired, and serve!
Enjoy your fluffy Japanese cheesecake!
