In a medium bowl, combine graham cracker crumbs and sugar. Pour in melted butter and stir until combined.

Press the crumb mixture into the bottom of a 6-inch or 7-inch springform pan.

Place the springform pan on a piece of aluminum foil and wrap the foil tightly around the bottom of the pan to prevent water from getting in.

In a large bowl, beat the softened cream cheese and sugar until smooth.

Beat in the eggs one at a time, mixing well after each addition.

Stir in the sour cream, vanilla extract, and lemon zest (if using).

Pour the filling over the prepared crust.

Pour 1 cup of water into the inner pot of your Instant Pot.

Place the prepared springform pan on top of a trivet inside the Instant Pot.

Secure the lid and set the valve to sealing. Cook on manual/pressure cook high for 35 minutes.

Once the cooking time is complete, allow a natural pressure release for 10 minutes before carefully releasing any remaining pressure.

Carefully remove the cheesecake from the Instant Pot and place it on a wire rack. Let it cool for about 1 hour.

Cover the cheesecake with plastic wrap and refrigerate for at least 4 hours, or preferably overnight.

Run a knife around the edge of the pan before removing the sides of the springform pan. Slice and serve.