Preheat the oven to 160C/325F/Gas 3. Lightly oil a 25cm/10in loose-bottomed round cake or spring-release tin, and line with greased greaseproof paper.
Mix together the ingredients for the base, spread over the base of the tin and press down firmly with the back of a metal spoon. Leave to set.
For the cheesecake, measure the margarine, sugar, curd cheese, flour, lemon rind and juice, and egg yolks into a large bowl. Beat until smooth. Fold in the cream. Whisk the egg whites stiffly then fold into the mixture. Pour on to the biscuit crust.
Bake in a preheated oven for about 1½ hours or until set. Turn off the oven and leave the cheesecake in the oven for a further 1 hour to cool. Run a knife around the edge of the tin to loosen the cheesecake and push the base up through the cake tin. Remove the side paper.
For the topping add the rhubarb, sugar, water and vanilla essence to a pan and boil it up, leaving on a high heat for 20 minutes, until the rhubarb has completely broken down. Take off the heat and leave over a bowl of ice to completely cool down.
Meanwhile soak the gelatine in cool water until soft, and mix it into the rhubarb compote. Pour the compote over the cheesecake pile on top of the cheesecake, levelling out evenly and place in the fridge to set for a couple of hours.