Preheat the oven to 180°C (356°F).
Melt the margarine, let it cool, and blend with the carrot in a blender or food processor until you achieve a puree.
In a bowl, combine the carrot puree and mix while alternately adding sugar, eggs, flour, vanilla extract, cinnamon, baking powder, raisins or almonds, and lastly, the orange juice.
Grease a cake mold with butter and sprinkle some flour on its sides (this prevents the cake from sticking). Pour the mixture evenly.
Bake at 200°C (392°F) for 40-45 minutes (check readiness by inserting a knife or skewer into the cake; if it comes out dry and clean, it's ready).
Allow the cake to cool before unmolding, decorate as desired, and serve.