Rub lemon zest into caster sugar using your fingers to release the oils for extra lemony flavor.
Whisk in cornflour, then add cream cheese and beat for 3–5 minutes until smooth and the sugar dissolves.
Add the beaten egg, lemon juice, and vanilla, and mix until combined.
Pour in the heavy cream and mix on low just until incorporated—don’t overmix to avoid air bubbles. Tap the bowl gently to release any that remain.
Wrap the outside of your springform pan in foil and place it in a larger dish. Pour the batter over the cooled base.
Add boiling water to the outer dish, filling it halfway up the cheesecake pan (be careful not to get water inside).
Bake for 60–90 minutes, until the edges are set and the center still has a slight wobble.
Let it cool at room temperature for 2 hours, then chill in the fridge for at least 6 hours or overnight.