Preheat the oven to 170°C. Grease or line a medium loaf tin with parchment paper/case.
In a bowl, mix the flours, baking powder and salt.
In another bowl, beat the sugar with the eggs until pale, then add the coconut oil. Add the flour mixture gradually, then add the yogurt and combine until you get a smooth batter.
Transfer the batter to the tin, spreading it out evenly. Scatter the shredded coconut pieces on the top ( if used), then put the tin in the middle of the oven.
Bake for 45-60 minutes, or until a toothpick inserted in the centre comes out clean. You might need to cover the tin with foil after 20-30 minutes, if the top of the cake looks brown already.
Allow to cool for 5 minutes in the pan, then transfer it to a wire rack.
Let it cool completely before slicing it.