Preheat the oven to 350F/175C and line an 8"x8" baking tray with parchment paper.

Place the crushed graham crackers or Digestives into the bowl of a food processor with the melted butter and process for 30 seconds until all the liquid has been absorbed.

Press the buttery crumbs into the bottom of the lined baking tin to form a base.

Rinse out the bowl of the food processor with cold water and add in the cream cheese, yogurt, Truvia, vanilla, egg, lemon juice and lemon zest. Process for 30 seconds, until all the ingredients are totally combined. Pour the cheesecake filling on top of the base.

For the raspberry swirl, add the raspberries, water and Truvia into a small saucepan over a medium-high heat. Mash the raspberries with the back of a spoon and cook for 5-10 minutes, until the mixture is thick and syrup-like.

Spoon large dollops of the raspberry swirl in random places on top of the cheesecake filling then take the same spoon and carefully use it to swirl the dollops together, creating a messy marbled pattern.

Place the baking tray in the preheated oven and bake for 20 minutes. Leave the cheesecake bars to cool to room temperature for 1 hour before storing in the fridge for at least 4 hours. When totally chilled, slice the bars into 9 and serve.