Microwave white chocolate at half power until melted.
Microwave cream cheese 30 seconds; whip until smooth.
Add sugar, sour cream, vanilla, lemon juice, and salt; whip smooth.
Sift and add cornstarch; mix thoroughly.
Add melted white chocolate; mix well.
On low speed, add eggs one at a time, mixing between additions.
Layer: half batter, half sauce, remaining batter, remaining sauce.
Create swirls using a skewer or butter knife.
Place cheesecake in a roasting pan filled halfway with boiling water.
Bake 70 minutes at 325°F.
Turn off oven; crack door 1" open for 1 hour.
Cool at room temperature 2–3 hours.
Refrigerate uncovered 8 hours or overnight.
Run a knife around edges before serving.