Preheat the oven to 350°F (175°C). Grease and flour a 9-inch round cake pan.

In a large mixing bowl, whisk together the dry ingredients: flour, baking powder, baking soda, salt, cinnamon, and nutmeg.

Add the wet ingredients: oil, sugar, eggs, and vanilla extract. Mix until well combined.

Fold in the grated carrots and crushed pineapple. If using, add the walnuts and raisins.

Pour the batter into the prepared cake pan and smooth the top.

Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.