Cut the whole orange into small pieces. Put the oil and eggs in a blender and mix for about 3 minutes. Mix the flour and sugar in a bowl, then add the contents of the mixer with a wooden spoon or whisk and stir in. Finally add the baking powder and stir in. Pour into a ring cake tin that has been greased and dusted with flour. Bake in the preheated oven for 35 to 40 minutes at 175 ° top / bottom heat.