Preheat the oven to 350 degrees Fahrenheit. Line an 8 x 8-inch baking pan with parchment paper and set aside.
In large bowl, add ½ cup melted salted butter and 1 cup packed light brown sugar. Stir until mixed and then add 1 large egg and ½ tablespoon vanilla extract. Stir vigorously until completely smooth.
Add 1 cup all-purpose flour and beat until batter is completely smooth and well combined. Stir until the batter pulls away from the bowl; add 1 cup white chocolate chips and ½ cup dried cranberries. Mix until just combined.
Spoon batter into prepared pan and bake 20-25 minutes or until a toothpick when inserted into the center of bars should come out mostly clean. Remove from oven and sprinkle with Optional: sea salt if desired. Allow blondies to cool completely before slicing into squares.