Put the biscuits in the food processor and pulse until they are powdered. Add the butter and work the mixture with your fingers until it reaches the crumb stage. Place it in a 20 cm springform cake tin. Using the back of a metal spoon or your hands pack it down flat and even. Bake it at 180ºC, in a preheated oven, for 10 minutes. Then remove from the oven and allow to cool. Meanwhile combine the crème fraîche with the icing sugar and beat well with an electric whisk until creamy and smooth. Add the cream cheese and lemon zest and beat, on slow speed, until they incorporate. Spoon the cream gently over the baked biscuit base and place it in the fridge for at least 1h to set. Drain the sour cherries compote in a colander and collect their syrup. Put it in a small pan over medium to low heat and add the corn flour. Stir constantly for 3-5 minutes until it reduces. Remove from heat and add the drained sour cherries. Leave the sauce to cool down completely and then spread it over the filling. Chill in the fridge for 30 minutes.