Blend softened butter into the crushed cookies and press the mixture into the bottom and up the sides (about an inch high) of the cake pan. Chill in the refrigerator while preparing the filling.

Preheat the oven to 300°F (without fan). In a mixing bowl, combine cream cheese, sour cream, sugar, and vanilla sugar until smooth.

Mix in eggs one at a time, ensuring each is well incorporated before adding the next. Stir in the orange juice, ensuring no seeds are left. Gently fold in the flour just until combined, then pour over the prepared crust.

Bake for about 60 minutes without opening the oven door.

While the cheesecake bakes, prepare the caramelized orange slices. Slice the ends off the orange, then cut into thin slices, removing any seeds.

In a skillet, combine sugar, water, and lemon juice. Bring to a simmer, add the orange slices in a single layer, cover, and simmer for 5 minutes on low heat. Remove the lid and continue simmering for another 15 minutes.

Allow the baked cheesecake to cool in the pan for about 10 minutes, then arrange the caramelized orange slices on top. Warm the remaining syrup and drizzle over the cheesecake.

Let the cheesecake cool to room temperature, then refrigerate for at least 4 hours before serving.