Heat oven to 350 F. Grease a 9×13-inch baking pan with cooking spray and line it with parchment paper, allowing 2 long sides to hang over the edges of the pan.

In a large bowl, whisk together the butter and brown sugar until light and fluffy, about 3 minutes. Add the eggs, one at a time, whisking to incorporate between each addition. Whisk in the vanilla extract.

In a second large bowl, mix together the flour, baking powder, salt and ground cinnamon.

Using a rubber spatula, mix the dry ingredients into the wet ingredients in two additions, making sure there are no streaks of flour and the batter is smooth.

Stir in the cranberries and white chocolate until evenly distributed.

Pour the batter into the prepared pan and use a rubber spatula to smooth the top. Bake for about 25 minutes until golden brown and a toothpick inserted in the center comes out clean. Let cool on a wire rack for 2 hours.

Use the long sides of the parchment paper to lift the blondies from the pan. Cut the bars into eight equal squares, then slice the squares in half diagonally to create 16 triangles.

Fill a small fine-mesh sieve with powdered sugar and lightly dust the blondies.

Leftover blondies can be stored in an airtight container for up to 5 days.