Preheat your oven to 170C / 340F (fan off), 150C / 300F (fan on). Spray the bottom and side of a 22 x 33 x 5cm / 9 x 13 x 2.25-inch cake tin with oil spray and line with baking paper.
Carrot - Grate the carrots using a regular grater and set aside.
Combine dry ingredients - Add the all-purpose flour, baking powder, bicarb soda, salt, cinnamon, and shredded coconut to a medium sized mixing bowl and use a whisk to combine. Set aside.
Mix oil, sugar and eggs - To a separate bowl, add the oil and brown sugar. Mix until well combined. Then add the eggs one at a time, mix well each time.
Add dry ingredients - Add the dry ingredients and use a spatula to mix until well combined.
Finish batter - Next, add the walnuts, grated carrots, coconut, orange zest and orange juice and mix until well combined. The mixture will seem thick at first but as you mix it will thin out.
Bake - Pour the batter into your cake tin and spread out. Bake for 20 minutes or until a toothpick inserted into the center comes out clean.