Preheat the oven to 325°F (160°C). Line a 9x9-inch baking pan with parchment paper, leaving some overhang for easy removal.

In a medium bowl, combine graham cracker crumbs and melted butter. Mix until the texture resembles wet sand. Press the mixture firmly and evenly into the bottom of the prepared baking pan.

In a large mixing bowl, beat softened cream cheese with a hand or stand mixer on medium speed until smooth. Gradually add sugar, mixing until fully incorporated. Add eggs one at a time, beating well after each addition. Finally, mix in sour cream and vanilla extract until the filling is creamy and uniform.

Pour the cream cheese filling over the prepared crust and spread evenly. Drop spoonfuls of warmed raspberry jam over the filling and use a knife to gently swirl the jam into a marbled pattern. Bake for 35-40 minutes, or until the edges are set and the center is slightly jiggly.

Allow the cheesecake to cool completely in the pan on a wire rack. Cover with plastic wrap and refrigerate for at least 2 hours to fully set.

Lift the cheesecake from the pan using the parchment overhang. Slice into squares with a sharp knife, dipping the knife in hot water and wiping it clean between cuts for neat slices. Serve cold.