Prep the pan. Heat the oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment, leaving overhang for easy lifting. Lightly grease the parchment.
Mix the wet ingredients. In a large bowl, whisk the melted butter with the brown and granulated sugars until smooth.
Add eggs and vanilla; whisk until glossy and combined.
Combine the dry ingredients. In a separate bowl, whisk the flour, baking powder, and salt.
Bring it together. Add the dry ingredients to the wet and stir just until no dry streaks remain. Fold in dried cranberries, white chocolate chips, orange zest, and orange juice. Do not overmix.
Bake. Spread the batter evenly in the pan.
Bake for 20–25 minutes, until the edges are set and lightly golden and a toothpick comes out with a few moist crumbs.
Cool completely. Set the pan on a rack and let the bars cool fully in the pan. This helps them set and slice cleanly.
Glaze. Whisk powdered sugar, orange juice, and a pinch of salt until smooth and pourable. Drizzle over the cooled bars.
Sprinkle a few extra white chocolate chips or chopped dried cranberries on top, if you like.
Slice and serve. Use the parchment to lift the slab out. Cut into squares or triangles. For the neatest edges, wipe the knife between cuts.