Preheat the oven to 160°C. Crush the biscuits finely and mix with the melted butter. Press the mixture into the base of a greased 23 cm tart tin to form an even layer.
In a bowl, whisk together the sweetened condensed milk, eggs, cream, naartjie juice, and zest until smooth.
Pour the filling over the biscuit base and smooth the top with a spatula.
Bake the tart in the preheated oven for 35–40 minutes, or until the filling is just set and slightly wobbly in the centre.
Allow the tart to cool, then chill in the refrigerator for at least 2 hours before serving.
Allow the tart to cool, then chill in the refrigerator for at least 2 hours before serving.