Preheat the oven to 350°F (175°C).

Mix graham cracker crumbs, melted butter, granulated sugar, and salt in a bowl. Press this mixture firmly into a 9x13 inch baking pan. Bake for 8-10 minutes until golden brown, then allow it to cool completely.

Prepare the raspberry swirl by combining fresh or frozen raspberries, sugar, lemon juice, and cornstarch in a saucepan. Cook this mixture over medium heat for about 5-7 minutes until it thickens, then let it cool slightly.

Beat softened cream cheese in a large bowl until smooth and creamy. Gradually mix in sugar, then add eggs one at a time, followed by vanilla extract and sour cream, ensuring to mix just until combined.

Pour the cheesecake mixture over the cooled crust. Add dollops of the raspberry swirl on top and use a knife to create a beautiful marbled effect.

Bake for 30-35 minutes or until the edges are set and the center is still slightly jiggly. Turn off the oven and let the bars cool inside for about 1 hour with the door slightly cracked.

Refrigerate for at least 4 hours (overnight is best) before cutting them into bars, giving the flavors a chance to meld beautifully.