Preheat oven to 200c with rack in middle.
Stir together orange juice, lime juice, and sugar in a bowl. Add rhubarb and marinate for about 10 minutes, stirring it occasionally.
Combine the almond meal, custard and the orange zest and stir to combine.
Roll out the short crust pastry to about 2-3 mm onto a sheet of baking paper, you will need to have a baking tray which will fit the size of your tart. This process can be done free form or you can press the pastry into a fluted tin or spring form cake tin for flexibility when serving.
Combine the almond meal and the custard together in a bowl until smooth. Spread this onto your sheet of pastry and then press the rhubarb into the mixture.
When all of the rhubarb has been laid down onto the mixture, fold over the pastry onto the rhubarb pressing the pastry down gently as you go. Sprinkle the tart with the almond flakes. Brush the top of the border with egg wash and sprinkle with large crystal brown sugar.
Bake the tart for about 30- 45 minutes minutes until golden brown and the rhubarb is cooked through.
Place the rest of the marinade in a pot and bring to a simmer over moderate heat. Reduce until slightly syrupy about 15 – 18 minutes.
Transfer the tart to a rack. Brush rhubarb and pastry with glaze and serve.