Preheat the oven to 180 C (160 C fan). Grease the 8' x 8' square baking tin and line it with baking paper, with plenty of overhang (for easy removal of the cheesecake later).
Reserve a small handful of raspberries and set aside. Transfer the remaining raspberries into a small saucepan set over a medium heat and add 1 tablespoon of water. Cook for 5 minutes, or until berries have released their juices and start to fall apart. Remove from the heat and push the mixture through a fine sieve or strainer to get rid of the seeds, then return to the saucepan and cook for another 8- 10 minutes or until it has reduced by half in volume and you have a thick sauce. Set aside.
In a medium bowl, combine together the crushed biscuits and melted butter, until the mixture resembles the texture of the wet sand. Transfer the mix into prepared baking tin, and press firmly, using back of the spoon or measuring cup. Transfer to the oven and bake for 10 minutes. Remove from the oven and allow it to cool for 5 minutes.
Place the cream cheese, eggs, sugar, sour cream, vanilla, half of lemon zest and 1 tablespoon of lemon juice in a large bowl and using an electric mixer, mix it well to combine, until you have smooth batter. Pour the mixture over the biscuit base. Add little dollops of raspberry sauce on top, and use a toothpick or a knife to create swirls on top. Scatter the remaining raspberries on top and bake for 45 minutes, until the edges are golden brown, but there is still a little wobble in the middle of the bake.
Allow the cheesecake to cool completely, then transfer it to the fridge for at least couple of hours, or overnight. Remove from the fridge, and using the overhang baking paper, gently lift the cheesecake from the tin. Top it with the remaining lemon zest, cut into 9 square bars and enjoy!
Bring the ingredients to the room temperature at least an hour before.
Make sure to use full-fat cream cheese, as it creates better flavour and firmer texture. Using the reduced-fat cheese may result in your cheesecake not setting properly.
If no sour cream is available, use the same amount of double / heavy cream.
Your cheesecake should have a gentle wobble and jiggle in the middle, after baking.
Make sure to cool and chill the cheesecake before removing it from the tin and slicing it.