Preheat your oven to 160 C/325F. Zest and juice the lemon and set aside. Crush the digestive biscuits or graham crackers, then mix the crumbs with the melted butter. Line the bottom of a 21cm/9 inch springform pan with the crumb mixture, press in with a spoon and bake in the preheated oven for 10 minutes, set aside and cool.
Separate the egg yolks from the egg whites. Mix cream cheese, egg yolks, sugar, semolina or flour, lemon juice and vanilla with an electric mixer until well blended. In a separate bowl whip egg whites until soft peaks form and gently fold them into the cheese mixture together with lemon zest.
Pour the mixture into your springform pan, then wrap the bottom of your springform pan with a layer of aluminium foil to prevent water getting in. Set it inside a larger roasting pan filled with 1 inch of water.
Bake at 320 F/160C for 60-65 minutes until the edges are lightly browned and the centre is nearly set. Turn the heat off and leave it in the oven for additional 20-30 minutes. Then open the door of your oven and allow the oven come to room temperature with the cheesecake inside to prevent the top from cracking.( If your cheesecake still cracks, don’t worry, you will cover it with the lemon curd later.) Cool the cheesecake completely in the refrigerator overnight.