Preheat your oven to 190°C (375°F) and line a muffin tin with paper liners or lightly grease the cups.
In a large mixing bowl, whisk together the flour, sugar, baking powder, and salt until evenly combined. This creates a dry, airy base for your muffins.
Zest the orange, scraping the bright outer layer into the bowl, then set the zest aside. The citrus oils will add a lively aroma to the batter.
In a separate bowl, melt the butter and whisk in the eggs one at a time until the mixture is smooth and slightly frothy. Then, stir in the orange juice and orange zest, combining everything into a fragrant liquid.
Pour the wet mixture into the dry ingredients and gently fold together with a spatula until just combined. Be careful not to overmix — a few lumps are okay, and this keeps the muffins tender.
Gently fold in the cranberries, distributing them evenly throughout the batter. If using frozen cranberries, do not thaw to prevent bleeding into the batter.
Spoon the batter evenly into the prepared muffin cups, filling each about three-quarters full. If desired, sprinkle coarse sugar on top for a crunchy crust.
Bake in the preheated oven for 20-22 minutes, or until the muffins are golden brown and a toothpick inserted into the center comes out clean.
Remove the muffins from the oven and let them cool in the tin for about 5 minutes, then transfer to a wire rack to cool completely. Their tops should be crackly, and the inside moist and juicy.
Once cooled slightly, enjoy these muffins warm or at room temperature, perhaps with a pat of butter or a drizzle of honey for an extra treat.
