Preheat the oven to 195C (175°C fan)
Whisk eggs, double cream, sugar, zest, bicarb, and baking powder together
Gradually add melted butter to the mixture
Stir in juice and crumbled crisp filo
Pour into a lined baking tin and bake for 45–50 minutes
Meanwhile, make the syrup by boiling sugar, juice, zest, and cinnamon until reduced
Pour syrup over the hot pie and let it soak
Serve warm or chilled
