Preheat the oven to 190 ° C, gas mark 3, convection 170 ° C. Butter a coated, round, deep cake pan (23 cm).
Cut the whole orange with the peel into pieces. Remove all seeds, then grind the orange pieces in a blender to a fine puree.
Mix the butter with sugar, orange puree, eggs, flour, baking soda and almonds in the food processor for 10 seconds until a smooth dough is formed. Pour the dough into the prepared mold and smooth the surface.
Bake the cake for 25-30 minutes until it has risen and is brown. Let cool in the tin for 5 minutes before turning it onto a wire rack. Dust with icing sugar before serving.
PS. Muscovado sugar is available in every third world store or Asia shop.
Self-propelling flour is difficult to obtain here, so make it yourself: For 1 kg of flour there are 2 packets of tartar baking powder, 1 level teaspoon of baking soda, 2 pinches of salt and ½ teaspoon of ascorbic acid.