Pre‑heat oven to 350 °F and generously grease a 10‑inch Bundt pan.
In a large bowl, whisk together flour, baking powder, and salt.
Cream butter, brown sugar, granulated sugar and orange zest until pale and fluffy (~3 minutes).
Beat in eggs, sour cream and vanilla. The mixture may look slightly curdled; that's okay.
Alternate adding the dry ingredients and then milk plus orange juice, mixing just until combined. Fold in cranberries gently.
Pour half the batter into the pan, sprinkle the cinnamon sugar filling (brown sugar + cinnamon), then top with the remaining batter. Draw a shallow line down the center before pouring.
Bake for 55‑70 minutes or until a toothpick comes out clean with just a few moist crumbs. Cool in pan for 1 hour, then invert.
Whisk the confectioners’ sugar with orange juice to make the glaze. Drizzle over the cooled cake.
Slice and serve. For extra festivity, top with sugared cranberries or orange zest.
Notes
This cake keeps moist for days and freezes well for up to 2 months. Wrap tightly and thaw overnight before eating. Use fresh orange juice and zest for brightest flavor.