Preheat the oven to 350°F (175°C) and line a 12" x 9" baking tin with parchment paper.
Mix Wet Ingredients: In a large mixing bowl, whisk together melted butter, brown sugar, eggs, and vanilla extract until smooth.
Combine Dry Ingredients: In a separate bowl, whisk together the flour, baking powder, and salt.
Fold in Additions: Gradually add the dry ingredients to the wet mixture, stirring gently. Fold in the chopped white chocolate and raspberries carefully to avoid breaking the berries.
Bake: Pour the batter into the prepared tin and spread evenly. Bake for 35-40 minutes or until the top is golden and set. A skewer inserted should come out with a few moist crumbs.
Cool & Serve: Let the blondies cool in the tin before cutting into 9 bars. Enjoy!