Preheat the oven to 120°C / 250°F / Gas mark ½.
Line the base of a 20cm round spring form tin with greaseproof paper and set aside.
Using a food processor or a bag and rolling pin, crush the biscuits.
Tip into a bowl with the melted butter and mix well.
Push the biscuits into an even layer into the base of the cake tin and chill.
In another bowl use an electric whisk or food processor to beat the soft cheese with the sugar.
Beat in the yoghurt then the eggs one at a time.
Finally, beat in the lemon zest, lemon juice and flour.
Fold through two thirds of the raspberries, crushing them a bit to allow their juices to mix in then scrape over the top of the biscuit base and smooth the top.
Bake for 45 minutes then turn off the oven, leave the cake inside for another hour then cool at room temperature.
To serve, remove from tin, scatter with remaining raspberries and dust with the icing sugar.