Preheat oven to 350°F and lightly coat a loaf pan with nonstick spray or line with parchment.
In a bowl, whisk together flour, baking powder, and salt.
In a large bowl, add sugar and orange zest. Rub together with your fingers to release the orange oils. Add the butter and cream together until light and fluffy. Beat in egg, then stir in buttermilk and vanilla.
Pour flour mixture into wet mixture and stir until combined, but do not overmix. Fold in cranberries.
Pour batter into prepared pan. Bake for 50-60 minutes, or until golden brown and a toothpick inserted in the center comes out clean. Let cool in the pan briefly before removing and cooling completely on a wire rack.