Preheat your oven 350°F. Grease a standard (9x5 inch) loaf pan and set aside.
In the bowl of a stand mixer fitted with a paddle attachment, beat the butter until fluffy. Add the sugar and beat until fully incorporated. Add the eggs, one at a time to the butter sugar mixture, scraping down the sides of the bowl and continue to beat until the mixture is smooth and glossy.
Add the flour, xanthan gum (if using), baking powder, baking soda, and sea salt. Spin the blade a few turns to mix.
Add the milk, buttermilk, rosemary, orange zest and juice, and vanilla extract and beat until the mixture is smooth. Fold in the chopped cranberries.
Pour batter into your prepared baking dish and bake for approximately one hour, or until a toothpick inserted in the center comes out clean. Cool in the pan for 10 minutes. Slide a knife around the edge of the pan to loosen bread, then remove to a cooling rack to cool completely.
Once cool, drizzle with cranberry glaze and top with sugared cranberries and rosemary sprigs for garnish, if desired.