Cream the butter and sugar together in a large mixing bowl using an electric mixer on medium speed until light and fluffy, about 2-3 minutes. Don’t rush this step – proper creaming creates that perfect shortbread texture.
Add the vanilla extract, orange zest, and orange juice (if using) to the butter mixture and beat until well combined. The orange oils released from the zest will perfume the entire dough.
Whisk the flour and salt together in a separate bowl, then gradually add to the butter mixture on low speed, mixing just until the dough comes together. Overmixing will develop gluten and make your cookies tough.
Fold in the chopped cranberries gently with a spatula until evenly distributed throughout the dough. The pieces should be visible but not so large they make cutting difficult.
Shape the dough into a log about 2 inches in diameter on a piece of plastic wrap. Roll it up, twist the ends to seal, and refrigerate for at least 30 minutes or up to 3 days. Chilling is crucial for developing flavor and ensuring the cookies hold their shape.
Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper. This prevents sticking and promotes even browning.
Slice the chilled dough log into rounds approximately 1/4-inch thick and place them on the prepared baking sheet about 1 inch apart. They don’t spread much during baking.
Sprinkle the tops with coarse sugar if desired for a sparkling finish and extra crunch.
Bake for 12-15 minutes or until the edges are just barely turning golden. Shortbread should not brown significantly – watch carefully in the final minutes.
Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely. They’ll firm up as they cool.