In a bowl, mix almond flour, 1/2 cup powdered erythritol, and melted butter. Press into the bottom of a greased 7-inch springform pan.
In another bowl, beat cream cheese and 2/3 cup powdered erythritol until smooth. Add eggs one at a time, then mix in sour cream, lemon juice, lemon zest, and vanilla extract.
Pour the cream cheese mixture over the crust in the pan. Cover with foil.
Add 1 cup of water to the Instant Pot, place a trivet inside, and lower the cheesecake onto the trivet.
Close the lid, set to sealing, and cook on high pressure for 35 minutes. Allow natural pressure release for 10 minutes, then quick release.
Remove the cheesecake, cool, then refrigerate for at least 4 hours before serving.
Notes:
Ensure the cream cheese is softened to avoid lumps in the batter. Refrigerate the cheesecake for at least 4 hours to set properly.