Preheat the oven to 160°C or 320°F for fan-forced or 180°C or 356°F for conventional ovens
Grease and line a 25cm square cake tin. Grate carrots using the fine grater side
Sift flour, baking powder and soda into a mixing bowl. Add salt, cinnamon and nutmeg, then lightly stir with the whisk to combine.
Combine oil, sugars, and vanilla into a separate bowl with the whisk. Add eggs one at a time and whisk to combine after each addition.
Fold the dry ingredients into the wet ingredients a 3rd at a time.
Fold in the carrots and the walnuts until everything is well combined.
Pour the cake batter into the cake tin and place it in the centre of the oven rack. Bake for approx 40 to 45 minutes or until the skewer comes out clean.
Allow the cake to cool in the tin for 15 minutes, before turning it out onto a cooling rack.
Decorate with cream cheese frosting and walnuts. Store in the refrigerator until ready to serve.