Put the flour, castor sugar in a large bowl and mix together. Add the butter and rub together until the mixture resembles breadcrumbs. Add 1 egg yolk, the vanilla and 1 tbsp cold water, and mix together until it just starts to come together as a dough.
Tip the mixture onto a clean work surface and gently bring together with your hands.
Custard & Rhubarb
Put the vanilla beans scraped from the pod (or the paste) in a pan over a medium- high heat, add the milk, cream and bring to a simmer. Meanwhile, tip the egg, yolks, sugar and flour into a bowl and whisk together until smooth. Pour the milk over the
egg mixture, whisking to combine. Pour the custard back into the pan and cook very gently, whisking constantly, for 2-3 mins until thickened. Pass through a sieve into a bowl. Press a sheet of cling film onto the surface of the custard to stop a skin
On a lightly floured surface, roll out the pastry into a large rectangle big enough to line a 30 x 20cm fluted rectangular tart tin or a round one if you prefer. Roll the pastry onto the rolling pin and carefully drape it into the tin, carefully lifting and
pressing into the corners and edges. Roll your rolling pin over the tart tin, cutting off the excess. Chill for 30 mins or until the pastry is firm.
Heat oven to 170c/gas 4. Line the tart with a piece of crumpled baking parchment and fill with baking beans or rice and place on a baking tray. Bake for about 15 - 20 mins, then remove the parchment and the beans, and return to the oven for another 5 mins or until the base is golden brown.
Heat oven to 190C/170C fan/gas 5. Put the rhubarb batons in a small roasting tin (so that they are in one flat layer) and sprinkle over the sugar, the vanilla pod and its scraped out seeds, and the orange zest. Roast for 15-20 mins, or until the rhubarb has softened but is still holding its shape and a vibrant pink syrup has formed. Remove from the oven, discard the vanilla pod and allow to cool.
Beat the custard a little to loosen, then pour over the pastry and smooth with a spatula. Top with the roasted rhubarb, brushing a little of the syrup on top. Best eaten at room temp on the day!