Preheat oven to 350°F. Grease a 9x9 baking pan and line with parchment paper for easy removal of the blondies.
Melt butter in microwave, checking every 15 seconds. Once melted, stir in ⅓ of white chocolate until smooth. Let cool slightly.
½ cup salted butter, 4 oz. white baking chocolate
Beat eggs, sugars, lemon zest, and vanilla extract in a large bowl.
2 large eggs, ½ cup granulated sugar, ½ cup brown sugar, ½ teaspoon pure vanilla extract
Mix in the butter and chocolate mixture, followed by flour and salt until just combined.
½ cup salted butter, 1 cup all-purpose flour, 4 oz. white baking chocolate, ¼ teaspoon salt
Gently fold in raspberries and another ⅓ of your white chocolate chunks. Pour the batter into prepared pan and spread evenly.
⅔ cup raspberries, 4 oz. white baking chocolate
Bake in preheated oven for 28-30 minutes, or until a toothpick in the center of the pan comes out mostly clean. Allow to cool in pan for at least 10 minutes before removing from pan and cooling completely on a wire rack.
White Chocolate Ganache Topping
Melt remaining white chocolate chunks with heavy cream in microwave in 15-second intervals.
4 oz. white baking chocolate, 1 tablespoon heavy cream
Stir until smooth, and drizzle over cooled blondies.
Storing: These white chocolate and raspberry blondies will keep for a few days at room temperature, or refrigerated for up to 5 days. The blondies freeze well and can keep frozen, well wrapped, for about 2 months.