To make a very orangey orange cake, you need lots of finely grated zest from the topmost, most oily part of the peel. Make sure you use a sharp grater or you'll have more of the precious orange oil on your grater than in your cake.
Before you start grating, please get rid of the nasty stuff that's sprayed on oranges. I wash mine in boiling water, then give them a good scrub and a thorough rinse