Preheat the oven to 160C (320F) and line the bottoms of two 7” (17-18cm) round cake pans with parchment paper. You can also use this recipe to bake in two 6” (15cm) cake pans if you prefer a taller cake. The sides can be buttered and floured or lined with paper as well.
In a bowl, combine the flour, salt, cinnamon, nutmeg, baking powder, baking soda, and walnuts.
In the bowl of a stand mixer fitted with a whisk attachment (or use a hand mixer and a bowl), whip the eggs with white and brown sugar until pale and doubled in volume.
Add the melted butter and oil. Mix well.
Add the carrots, orange zest, and juice and mix again.
Fold in the dry ingredients using a rubber spatula.
Divide the cake batter between two cake pans and bake for 27 minutes or until a toothpick inserted into the center comes out clean.
Remove from the oven and let cool down in the pan until safe to handle. Then, transfer it onto a cooling rack to cool down completely before assembling the cake.