Preheat oven to 350 degrees F. Spray an 8″ square baking dish with cooking spray.
With an electric mixer, cream together butter and sugar on medium-low speed for about 3 minutes. Mix in egg and vanilla until smooth.
Add flour, baking soda, and salt, and mix on low until combined. Spread mixture into the prepared pan.
Heat cream cheese and jam in a microwave-safe bowl for 20-30 seconds. (You want them softened enough to stir together but not hot.) Stir them well, and spread cream cheese mixture on top of blondie dough. Use a spoon to swirl cheesecake into the blondies.
Bake in preheated oven for 30-35 minutes, until center is set. Allow to cool before cutting.