Preheat your oven to 375°F (190°C).

In a large mixing bowl, combine the powdered sugar, egg yolk, and melted butter, stirring until fully incorporated. Add the vanilla extract and all-purpose flour, then mix until a crumbly dough forms.

Press the crust mixture firmly into a 9 or 10-inch tart pan, ensuring an even layer across the bottom and up the sides. Use a fork to prick the surface.

Chill the tart pan in the freezer for about one hour.

Bake the crust for 15 minutes covered with foil. Remove the foil and bake for an additional 13–15 minutes until golden brown.

In a small bowl, combine the fresh lemon juice and unflavored gelatin. Allow the mixture to bloom, then microwave until melted.

In a large mixing bowl, beat the cream cheese until smooth. Gradually mix in the sweetened condensed milk, then add the melted gelatin mixture along with lemon zest.

Pour the creamy filling into the cooled crust, spreading it evenly. Cover with plastic wrap and refrigerate for at least 2 hours.

Warm the orange marmalade over low heat and add the fresh blueberries and blackberries, stirring to coat.

Carefully spoon the berry mixture over the chilled cheesecake and return it to the refrigerator for an additional 2 hours before serving.