Preheat the oven to 325°F (160°C).

In a mixing bowl, combine the graham cracker crumbs, granulated sugar, and melted butter. Mix until well combined.

Line the muffin tin with cupcake liners or grease it lightly. Press about 1 tablespoon of the graham cracker mixture into the bottom of each cup to form the crust, packing it tightly.

In another mixing bowl, beat the softened cream cheese with an electric mixer until smooth and creamy.

Add the granulated sugar and mix until well combined. Then add the eggs one at a time, mixing just until incorporated. Add the vanilla extract and lemon zest/juice (if using) and mix until smooth.

Spoon the cream cheese mixture over the crust in each cup, filling them about ¾ full.

Bake in the preheated oven for 20-25 minutes, or until the edges are set but the centers are slightly jiggly.

Remove from the oven and let them cool in the muffin tin for about 10 minutes, then transfer to a cooling rack to cool completely.

Once cooled, refrigerate the mini cheesecakes for at least 2 hours or until chilled and set.

Before serving, you can top the mini cheesecakes with fresh fruit, whipped cream, or chocolate drizzle for added flavor and decoration.