Preheat the Oven: Preheat your oven to 375°F. Line a standard 12-cup muffin pan with paper liners or lightly grease the cups.
Mix the Dry Ingredients: In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt until evenly combined.
Mix the Wet Ingredients: In a separate bowl, whisk together the melted butter, eggs, milk, fresh orange juice, orange zest, and vanilla extract until smooth and well combined.
Combine the Batter: Pour the wet ingredients into the dry ingredients. Gently fold with a rubber spatula just until combined. Be careful not to overmix, as this can make the muffins dense.
Add the Cranberries: Gently fold the fresh or frozen cranberries into the batter, spreading them evenly throughout without crushing them.
Fill the Muffin Pan: Divide the batter evenly among the prepared muffin cups. Fill each cup generously, leaving enough space for the muffins to rise.
Bake: Place the muffin pan in the preheated oven and bake for 18–22 minutes, or until the tops are lightly golden and a toothpick inserted into the center comes out clean or with a few moist crumbs.
Cool: Let the muffins cool in the pan for about 5 minutes. Transfer them to a wire rack and allow them to cool further.
Serve: Serve the cranberry orange muffins warm or at room temperature. Enjoy them with coffee, tea, fresh fruit, or a drizzle of optional orange glaze.