Preheat oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper.

In a bowl, mix graham cracker crumbs, melted butter, and sugar until combined. Press into the bottom of the baking pan and bake for 10 minutes. Let cool.

In a large bowl, beat cream cheese and sugar until smooth. Add eggs one at a time, mixing after each. Stir in vanilla extract.

Pour cheesecake filling over the cooled crust and spread evenly.

In a saucepan over medium heat, combine rhubarb, sugar, cornstarch, water, and lemon zest. Cook until rhubarb softens and mixture thickens (about 5 minutes). Let cool slightly.

Gently spoon the rhubarb mixture over the cheesecake layer, swirling slightly with a knife for a marbled effect.

Bake for 35-40 minutes or until the center is set. Cool to room temperature, then refrigerate for at least 4 hours before slicing.