Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners or grease it with cooking spray.
In a large mixing bowl, combine the vanilla cake mix and cinnamon (if using).
In a separate bowl, whisk together the orange juice, vegetable oil, eggs, and vanilla extract until well blended.
Slowly pour the wet ingredients into the dry ingredients, stirring until just combined. Be careful not to overmix; a few lumps are okay.
Gently fold in the cranberries, orange zest, and chopped nuts (if using) until evenly distributed.
Spoon the batter into the prepared muffin tins, filling each cup about two-thirds full.
Bake in the preheated oven for 18-22 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Once baked, remove the muffins from the oven and allow them to cool in the pan for about 5 minutes before transferring them to a wire rack to cool completely.
If desired, once cooled, dust the tops with powdered sugar for a sweet finishing touch.
Notes
Optional ingredients can be adjusted based on preference.