Grate the carrots and set aside 3 cups of them.
Sift the flour with the baking powder, baking soda and salt. Separately, beat the eggs with the sugar using a whisk.
To them, add the grated carrots, oil, raisins, coarsely ground walnuts and finely grated orange rinds.
Pour the mixture into a container with the flour and stir well.
Pour this into a form that you've laid out with baking paper and buttered.
Bake in a preheated 338°F (170 °C) oven for about 1 hour.
Once it cools, invert it into a suitable plate and sprinkle with powdered sugar.