Preheat the oven to 350°F (175°C).

In a large mixing bowl, combine all-purpose flour, baking powder, baking soda, cinnamon, and salt.

In another bowl, whisk together vegetable oil, granulated sugar, brown sugar, and eggs until well blended.

Stir in the grated carrots and walnuts into the wet ingredients.

Gradually add the dry ingredients to the wet mixture, mixing until just combined.

Pour the batter into a greased cake pan.

Bake for 40 minutes or until a toothpick inserted in the center comes out clean.

Allow to cool before serving.