Preheat the oven to 180°C/350°F. Peel the oranges. Chop one of them into small pieces, but thinly slice the other one whole for the final decoration. Squeeze yuzu for it's juice, and peel some of its skin a bit for zest. If you do not have Yuzu, lemon juice is ok.

Put margarine and sugar into a bowl and mix together well until you get a creamy texture.

Add the beaten eggs slowly into the bowl, and mix them very well. Add the chopped orange, yuzu juice and zest (or lemon alternative) then mix together.

Put flour, baking powder and salt into a bowl and lightly mix together, do not mix too much! A powdery mixture is fine.

Spread olive oil or margarine on the inside of the loaf pan, then pour in the mixture. Push down the centre of mixture a bit. Then lay on top the sliced oranges one by one, overlap a bit if you like. Bake for about 40 min. Check whether it's cooked or not by pushing a stick into the centre. If nothing comes out with the stick, then it's done. If not done, then bake for another 10 min. If surface is already baked, cover over with aluminum foil to avoid over browning.

note: you can use muffin cups instead of a loaf pan. In that case, bake them for about 20 min.