Set your oven to 350°F and position a rack in the center. Prepare a bundt pan by coating it with butter and flour, ensuring all excess is removed.
In a stand mixer or large bowl, whip eggs and granulated sugar on high speed for three minutes until the mixture turns pale.
Gradually incorporate the oil, followed by the melted butter, then vanilla extract, mixing thoroughly after each addition. Blend in the buttermilk until the mixture is smooth.
In a separate bowl, sift together the flour, baking powder, baking soda, and salt. Slowly mix the dry components into the wet mixture on low speed until just combined, avoiding overmixing.
Fold in the cranberries and orange zest gently until evenly distributed.
Transfer the batter to the prepared bundt pan, smoothing the top. Bake for 55 to 60 minutes, or until a toothpick inserted near the center emerges with a few moist crumbs. Let it cool in the pan for 15 minutes before inverting onto a wire rack. Allow to cool completely.
For the glaze, stir together powdered sugar, orange juice, and zest in a small bowl until smooth and thick yet pourable. Adjust the consistency as needed with additional juice or sugar. Drizzle over the cooled cake.
Optionally, top with sugared cranberries and extra orange zest before serving.