Preheat your oven to 325°F (163°C). In a mixing bowl, combine graham cracker crumbs, sugar, and melted butter, stirring until resembling wet sand. Firmly press into the bottom of a greased springform pan. Chill while preparing the filling.

In a large mixing bowl, beat softened cream cheese until smooth and creamy, about 2-3 minutes. Gradually add granulated sugar, mixing well after each addition. Incorporate eggs one at a time, blending until combined. Add vanilla extract, orange zest, orange juice, and sour cream, mixing until fluffy.

Remove crust from refrigerator, pour the filling over it, spreading evenly with a spatula. Prepare a water bath by placing the springform pan in a larger roasting pan, filling the outer pan with hot water until halfway up the sides of the springform pan.

Bake in the preheated oven for 50-65 minutes until edges are set but the center has a gentle jiggle. Turn off the oven and crack the door open slightly, letting cool inside for 30 minutes.

After cooling, remove from water bath, transfer to a cooling rack. Let it come to room temperature before refrigerating for at least 4 hours or overnight.

In a saucepan, combine cranberries, orange juice, and sugar over medium heat. Cook while gently stirring until cranberries begin to pop and break down, about 5-7 minutes. For a thicker sauce, mix cornstarch with water, stir in until thickened, then remove from heat and cool.

Once cheesecake is chilled, spread the cranberry topping evenly over the surface. Garnish with additional orange zest if desired.

Serve chilled, using a warm knife to ensure clean slices. Optionally, add a dollop of whipped cream.