Prepare the Crust:

Preheat your oven to 350°F (175°C). Line a 9x9-inch baking pan with parchment paper, leaving an overhang for easy removal.

In a food processor, grind the pistachios until fine. Combine them with graham cracker crumbs, sugar, and melted butter in a bowl. Press the mixture evenly into the bottom of the prepared pan. Bake for 8–10 minutes, then let it cool while you prepare the filling.

Make the Raspberry Sauce:

In a medium saucepan, combine raspberries, sugar, and lemon juice over medium heat. Cook, stirring occasionally, until the raspberries break down (about 5 minutes). Stir in the cornstarch slurry and cook for 1–2 more minutes until the mixture thickens. Strain through a fine-mesh sieve to remove seeds, if desired, and let it cool.

Prepare the Cheesecake Filling:

In a large bowl, use an electric mixer to beat the cream cheese and sugar until smooth. Add the eggs one at a time, mixing well after each addition. Mix in the vanilla extract and sour cream until fully combined.

Assemble the Bars:

Pour the cheesecake filling over the cooled crust, spreading it into an even layer. Drop small dollops of the raspberry sauce on top of the filling. Use a toothpick or skewer to gently swirl the sauce into the filling, creating a marbled effect.

Bake the Bars:

Bake in the preheated oven for 30–35 minutes, or until the edges are set and the center is slightly jiggly. Allow the bars to cool to room temperature, then refrigerate for at least 4 hours or overnight.

Slice and Serve:

Once chilled, lift the bars out of the pan using the parchment paper overhang. Slice into squares or rectangles and serve. Optionally, garnish with chopped pistachios and fresh raspberries.