Whisk together the flour, baking powder, baking soda, salt, and cinnamon in a large bowl. Beat in the sugar, oil, and eggs. Once well combined and creamy, stir in the carrots, crushed pineapple, and walnuts.
Generously grease two 9-inch cake pans with non-stick spray. (You can also use a 9x13 baking dish and add 20 minutes to the baking time)
Bake for 35 minutes, or until a toothpick inserted in the center comes out clean. Once out of the oven, let cool completely.
Top with your favorite cream cheese frosting or use my recipe in this cookbook!