Preheat your oven to 180°C (350°F).
Lightly grease a 9-inch (23 cm) with butter, and dust it with a bit of flour --- then set aside.
Strain the flour and baking powder into a medium-sized bowl.
Chop the oranges into quarters (or smaller chunks if using a large orange) and place them in the food processor.
Pulse/Process until you no longer see big chunks of oranges.
Mix eggs and sugar in a large bowl until you get a pale-colored batter.
Add olive oil and continue mixing.
Add the pureed orange and mix to combine everything evenly.
Add the sifted flour and baking powder from earlier and mix gently (just enough to combine).
Pour your Sicilian orange cake batter into the prepared cake pan.
Place the pan in the middle of the oven for 40 to 45 minutes or until a toothpick comes out dry when inserted into the cake.
Set aside at least ten minutes to cool, then sprinkle with powdered sugar.
Your Sicilian orange cake is now ready for serving --- and slicing!