Pour the water into the Instant Pot bowl and set a steamer rack or trivet in the bottom.
Wrap a piece of foil around the bottom of a 6- or 7-inch springform pan to prevent water from getting into the pan and the cheesecake from seeping out. (You can also use a heat-proof dish.) Grease the inside of the pan with coconut oil.
In a medium-size bowl, beat the cream cheese and sweetener until smooth and creamy (about 2 minutes).
Add the eggs, vanilla, lemon zest, and lemon extract (if using), and beat briefly until combined.
Transfer the mixture to the springform pan and place it on the steamer rack in the Instant Pot.
Secure the lid and move the vent knob to the sealed position.
Select “Manual” and cook for 20 minutes. Once the cooking time is up, release the steam naturally.
Dab any moisture on top of the cake with a paper towel.
Refrigerate the cheesecake for at least 2 hours before removing from the springform pan prior to serving.
Cut into slices and serve chilled.