Preheat the oven to 180°C.
First, roll pastry out on a lightly floured surface and using a 20 cm diameter pastry dish or circle dish as a template, cut 2 discs of pastry (1x 18cm , 1x 20cm). If possible, one larger of 1-2 cm diameter than the second to place over the mixture later. Place them on a baking tray lined with parchment paper and transfer in the fridge until required.
Next, prepare the almond cream, mix the icing sugar, ground almonds, corn flour and butter together until light and creamy. Using a wooden spoon, combine the eggs, and rum until smooth and well combined. Transfer in a piping bag and Allow to set in the fridge for 20-30 minutes if possible.
Once set, remove the almond mixture and pastry from the fridge.
Place the smallest pastry disc on a baking tray lined with parchment paper.
Pipe or spoon the almond cream into the centre of the pastry base, leaving approximately 2 cm around the edge. Brush the edges with some egg wash.
Then, carefully, line the second layer of pastry over the almond mixture. Create a small hold in the center to let steam escape while baking.
Gently press the edges to seal fully. Using a knife, press the pastry vertically to create a design all around the tart. If possible, again, Place in the fridge for 20 minutes to set.
Once ready to bake, remove from the fridge and brush the pastry with egg wash.
With the back of a knife, draw curves going from the middle of the pie to the edge. Place the tart in the oven and bake for 35 to 45 minutes, until cooked through and golden.
Remove from the oven and brush with some cooled syrup or sprinkle with icing sugar. Transfer onto a rack and allow to cool for a few minutes.
Serve warm or at room temperature.