In a smaller bowl, zest 1 orange with a fine grater, then juice the oranges until you have ¾ cups of orange juice. Whisk in egg and oil. In a larger bowl sift together the flour, sugar, baking powder, baking soda, and salt. Add wet ingredients to dry ingredients and mix just to moisten (keep it to no more than 12 turns with your spoon otherwise your batter will get tough). In a separate bowl mix cranberries with 1 tbsp flour then fold into the muffin batter.
Fill muffin liners until about ¾ full. Sprinkle with course sugar if desired. Put muffins in the oven and increase temperature to 400°F. Bake for 16-18 minutes, until tops are lightly browned and an inserted toothpick comes out clean. Let cool for 5 minutes in tin then remove from tin to continue cooling. Enjoy!