Pumpkin Spice Blondies with Cheesecake Swirl

Make the Cream Cheese Topping: Microwave the cream cheese in a medium microwave-safe bowl in 15 second bursts, stirring until smooth but not hot. Whisk in the sour cream, flour, sugar, vanilla, and salt until smooth, set aside while you make the blondies. Make the Blondie Base: Preheat the oven to 350 degrees F. Butter the pan and line with parchment, leaving a 2" overhang. Whisk the flour, pumpkin spice, and salt in a small bowl until well combined. In a separate large bowl, whisk the melted butter and brown sugar until smooth. Whisk in the egg and vanilla extract. Scrape the sides and bottom of the bowl with a rubber spatula. Whisk in the pumpkin puree and scrape the sides down again. Whisk in the flour mixture until no streaks remain. Reserve about 1/2 cup of the blondie batter and spread the rest evenly in the prepared pan. Spread the cream cheese topping on top of the blondie batter, leaving a 1/2" border. Dollop the reserved blondie batter over top, then use a chopstick, butter knife, or toothpick to swirl the blondie batter and cream cheese layers together. Be careful not to overmix—the idea is to get pretty swirls of the two without combining them too much. Bake the blondies until a toothpick inserted in the center comes out with just a few crumbs, 40 to 50 minutes. Cool completely in the pan, then cut into bars and serve.