Prep the pan and oven: Preheat oven to 350°F (175°C). Line a 9x5-inch loaf pan with parchment, leaving overhang for easy removal.
Lightly grease.
Mix dry ingredients: In a bowl, whisk flour, baking powder, and salt. Set aside.
Infuse the sugar: In a large bowl, rub orange zest into the sugar with your fingertips until fragrant. This releases the oils for a stronger orange flavor.
Combine wet ingredients: Add melted butter, oil, eggs, vanilla, buttermilk, and orange juice to the zesty sugar.
Whisk until smooth.
Bring the batter together: Add dry ingredients to wet and gently whisk or fold until just combined. Do not overmix.
Prepare cranberries: Toss cranberries with 1 tablespoon flour. Fold into the batter with a spatula.
Reserve a few for the top if you like.
Fill the pan: Scrape batter into the prepared pan. Smooth the top and dot with reserved cranberries.
Bake: Bake for 55–65 minutes, until a toothpick inserted in the center comes out clean or with a few moist crumbs. If browning too quickly, tent loosely with foil for the last 10–15 minutes.
Cool: Let the loaf cool in the pan for 15 minutes, then lift out and cool completely on a rack.
Glaze: Whisk powdered sugar with orange juice until smooth and pourable.
Drizzle over the cooled loaf. Add a pinch of zest if you want extra zing.