Preheat your oven to 325°F (163°C). Line a muffin tin with paper liners for easy removal.

In a medium bowl, mix together the graham cracker crumbs, sugar, and melted butter. Stir until the mixture resembles wet sand.

Using your fingers or the back of a spoon, press the crumb mixture firmly into the bottom of each muffin liner. Bake in the preheated oven for about 5 minutes. Remove and let cool.

In a large mixing bowl, beat the softened cream cheese with a hand mixer on medium speed until smooth and creamy.

Gradually add in the sugar, then mix in the eggs one at a time, beating well after each addition. Finally, add in the vanilla extract and lemon zest, if using.

Spoon the cream cheese mixture over the cooled crusts, filling each liner about 3/4 full.

Place the muffin tin back in the oven and bake for 18-20 minutes or until the edges are set but the center still has a slight jiggle.

Let the mini cheesecakes cool to room temperature, then refrigerate for 2-4 hours before serving.