Rhubarb and Pistachio Frangipane Tart

Rub together the flour, salt and cold butter in a bowl until the mixture has a breadcrumb-like texture (or blitz in a food processor). Stir in the sugar and gradually the beaten egg to form a soft, pliable dough (you will not need all the egg). Wrap the dough in clingfilm and chill for 30 minutes.

Roll out the pastry on a lightly floured surface to a thickness of 3-5mm and use it to line a 23cm loose-bottomed tart tin, leaving a little excess pastry to hang over the edges. Return to the fridge for 20 minutes.

Preheat the oven to 240C/220C fan/gas 8.

Line the chilled pastry case with baking parchment and fill with baking beans (or rice). Sit the tart case on a baking sheet and bake for 5 minutes. Reduce the oven temperature to 200C/180C fan/gas 6 and bake the tart case for a further 10-15 minutes, until it starts to turn golden and become firm. Remove the baking beans and parchment, brush with the egg yolk and return to the oven for a further 5 minutes, until evenly golden. Remove from the oven and allow to cool slightly. When cool enough to handle, trim away the excess pastry with a sharp knife.

Put the caster sugar and grenadine in a large saucepan. Top up with 400ml water and bring to a simmer over medium-high heat, stirring to dissolve the sugar. Place the rhubarb pieces in the hot liquid and simmer for 3 minutes, then remove the pan from the heat and allow the rhubarb to continue to cook in the liquid for 5 minutes. Carefully transfer the rhubarb from the liquid into a bowl using a slotted spoon and place in the fridge to cool. Place the saucepan of cooking liquor back on the heat and bring to a rapid boil. Boil until syrupy – keep a close eye on it towards the end to prevent it burning. Remove from the heat and set aside.

Beat together the sugar and butter in a bowl until light and creamy. Add the eggs one at a time, beating well after each addition. Put the pistachios in a blender and pulse until they have a breadcrumb-like texture, then mix them into the butter mix with the salt.

Spread the frangipane on the bottom of the pastry case then gently press in the cooked rhubarb pieces. Bake in the oven for 45-50 minutes, until deep golden and the frangipane has just set in the centre. Remove from the oven and leave to cool to room temperature before removing the tart from the tin. Warm the reduced rhubarb cooking liquor and brush it over the tart before serving.