Preheat your oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or lightly grease each cup.

In a large mixing bowl, whisk together the flour, sugar, baking powder, and salt. Set aside.

In a medium bowl, combine the orange juice, orange zest, oil (or melted butter), and eggs. Whisk until smooth.

Gradually pour the wet mixture into the bowl of dry ingredients. Use a spatula or wooden spoon to gently fold the batter until just combined. Be careful not to overmix—it’s okay if a few streaks of flour remain.

Toss the cranberries with a teaspoon of flour (to prevent them from sinking in the batter), then gently fold them into the mixture.

Divide the batter evenly among the prepared muffin cups, filling each about 3/4 full. If desired, sprinkle the tops with coarse sugar for a crunchy finish.

Bake in the preheated oven for 18–22 minutes, or until the tops are golden and a toothpick inserted into the center comes out clean.

Let the muffins cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.