Preheat the oven to 180°C / 350°F / gas 4.
Line your muffin tins with paper cases or lined greased tins
Grate the carrot, grate the skin of the orange on the fine side of the grater then cut the orange in half and squeeze out the juice.
Cream the butter and the sugar together in a mixing bowl, whisk in the eggs. Stir in the flour and baking powder, add all the remaining ingredients and mix thoroughly.
Fill the paper cases with the cake mixture. Bake in the preheated oven for 20 to 25 minutes. Check to see whether they are cooked properly by sticking a wooden skewer or a knife right into one of the cakes – if it comes out clean, they’re done. If it’s a bit sticky, pop them back into the oven for a little longer. Remove from the oven and leave the cakes to cool on a wire rack.