Preheat oven to 350°F. Lightly spray the bottom and sides of an 8-inch square pan with nonstick cooking spray; line with parchment paper, and lightly spray again.
In a large bowl, stir together butter and brown sugar until smooth. Add egg and vanilla and stir to combine. Stir in flour and salt, just until combined.
Stir in half of raspberries, and all but a tablespoon or two of white chocolate chips.
Spread batter into prepared pan. Sprinkle top with remaining raspberries and white chocolate chips. Bake for 30 to 35 minutes or until a toothpick inserted in the middle comes out with moist crumbs. The blondies will be slightly browned around the edges. Cool for at least 20 minutes in the pan before lifting the blondies out by the parchment paper. Set on a wire rack to finish cooling before slicing and storing in an airtight container. I recommend storing in the fridge if storing for more than 1 day.