To make the tart dough, place the butter in a large food processor bowl fitted with a metal blade. Process until smooth and creamy, scraping down the sides with a rubber spatula as needed.
Add the icing sugar and process until well blended.
Add the ground almonds, salt, egg, and vanilla - and process until smooth, scraping down the sides of the bowl as necessary.
Add the flour and pulse the mixture until it just starts to form a ball and stop. Remove the mixture from the food processor bowl and place onto cling film and form into two flat discs. Wrap each disk separately and refrigerate for at least 4 hours.
Once chilled, remove 1 portion of dough from the refrigerator and roll out between 2 sheets of baking paper until 3mm thick.
Carefully place the dough into a 24cm tart tin and press the dough against the bottom and edges of the tin to ensure it is well fitted. If the dough cracks or splits simply patch with additional pastry. Trim the top of the tart - the easiest way to do this is to roll the rolling pin over the top of the tart case which will trim the edges neatly.
Refrigerate for at least 30 minutes and repeat with the second portion of dough.
Preheat the oven to 180 degrees celsius (350 Fahrenheit) and line the tarts with baking paper and add dried beans or pastry weights and bake for 20 to 25 minutes until lightly coloured.
Set aside while you make the filling.
TART FILLING:
Preheat the oven to 180 degrees celsius (350 Fahrenheit) and add the oranges, cornflour, and sugar to a large bowl of a food processor and process until thoroughly pureed and smooth.
Add the egg, egg yolk and melted butter and pulse to combine.
Pour into the tart shells and bake for 15 to 20 minutes or until the filling is bubbling and lightly browned.
Remove from the oven and cool for at least 20 minutes before removing from the pan.
Serve at room temperature with whipped cream.
Notes
When working with the tart dough, if you find the pastry becomes too soft or sticks to the baking paper, place in the refrigerator for 10 to 15 minutes.