For the rhubarb curd
360g of trimmed rhubarb cut into 2cm chunks
50g golden caster sugar
2 tbsp grenadine
2 tbsp of cornflour
2 egg yolks
50g melted, unsalted butter
1. Mix the rhubarb with the sugar and grenadine in a pan and heat gently for around 12 minutes, until the rhubarb starts to break down. Remove and then purée in a food processor before returning to the pan.
2. Mix the cornflour with a bit of the rhubarb purée to make a paste and then return to the pan and bring to the boil. Allow it to boil for one minute.
3. In a bowl, whisk the yolks with the butter and the rhubarb mixture and cover before allowing to cool completely. Preheat the oven to 180C/gas 4.
For the base
60g unsalted butter (plus extra for greasing)
200g digestive biscuits
1. Butter a 22cm, loose-bottomed sandwich tin and line the base with baking paper.
2. Melt the butter in a pan and crush the biscuits into fine crumbs in a bag with a rolling pin. Mix together and then add to the sandwich tin, pressing down to ensure a firm, even layer. Chill in the fridge for 20 minutes.
For the cheesecake mixture
600g full-fat cream cheese
Grated zest of two lemons
3 eggs and two beaten yolks
100g soured cream
2 tbsp plain flour
1. Beat the mascarpone and cream cheese with an electric mixer until really smooth. Add the sugar and continue to whisk for a few minutes.
2. Beat in the lemon zest and flour, followed by the beaten eggs a little bit at a time and then fold the soured cream through the mixture.
3. Spoon layers of the cheesecake mixture and rhubarb curd into the tin and ripple the top with a skewer. Bake for 50 minutes.