Preheat your oven to 350°F (175°C). Line two large baking sheets with parchment paper.
In a large bowl using an electric mixer, beat the softened butter, granulated sugar, and brown sugar on medium-high speed for 2-3 minutes, until light and creamy.
Add the egg, vanilla extract, and orange zest (if using). Beat on medium speed until just combined.
In a separate medium bowl, whisk together the all-purpose flour, baking powder, and salt.
Add the dry ingredients to the butter mixture and mix on low speed until the dough just comes together. Do not overmix.
Using a spatula, gently fold in the white chocolate chips and cranberries until they are evenly distributed throughout the dough.
Drop rounded tablespoons of dough about 2 inches apart onto the prepared baking sheets. A small cookie scoop works well for this.
Bake for 12-15 minutes, or until the edges are lightly golden and the centers are set. The bake time may be slightly shorter if using dried cranberries.
Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.