Preheat oven to 350°F (175°C) and line a 9x13-inch baking pan with parchment paper.
In a large bowl, combine melted butter and brown sugar until smooth. Add eggs and vanilla extract, and whisk until fully incorporated.
In a separate bowl, mix flour, baking powder, and salt. Gradually fold the dry ingredients into the wet mixture until just combined.
Stir in white chocolate chips and cranberries, ensuring they are evenly distributed.
Pour the batter into the prepared pan and smooth the top with a spatula.
Bake for 25-30 minutes, or until the edges are golden and a toothpick inserted into the center comes out mostly clean.
Allow blondies to cool completely in the pan before slicing into squares.