FOR THE CRUST:
Crush graham crackers until fine. You can use a blender for speed.
Melt butter in microwave in 20 second intervals or melt slowly in a pan.
Combine crumbs and sugar, then pour in butter and mix well until all the crumbs are coated with butter.
Butter the bottom of a springform cheesecake pan, line with parchment paper, and press the crumb mixture evenly into the bottom.
Freeze until ready to use.
FOR THE FILLING:
If using frozen dragon fruit, thaw first. Puree fruit and set aside.
Sprinkle gelatin over water and stir after 10 seconds. Let bloom for 3 minutes.
Melt one bar of white chocolate in a microwave-safe glass or ceramic bowl in 15-second intervals, stirring after each interval, 1 to 3 minutes.
Using a stand mixer, beat cream cheese and sugar together until creamy. Mix in the melted white chocolate, egg, lemon zest, gelatin, and vanilla extract until creamy.
Divide mixture into 2 parts and pour one half into the pie crust and return to freezer for at least 20 minutes.
Combine remaining half with dragon fruit mixture and pour on top of plain cheesecake. Return to freezer for at least one hour.
Bring heavy cream to a boil in a saucepan. Pour over the remaining chopped white chocolate and stir until smooth. Pour over the cheesecake and cover evenly by tilting and turning the pan.
Refrigerate until ready to serve.