Method
Preheat oven to 350°F (177°C). Grease a 9x11 dish for baking. (Can also work with 2 x 9" pans if you wanted to make a layered cake.)
Whisk flour, cinnamon, nutmeg, baking soda, and salt together in a bowl.
In a separate large bowl, whisk together the vegetable oil, granulated sugar, and brown sugar.
Add eggs to the oil and sugar mixture one at a time, mixing until smooth after each addition.
Fold the finely grated carrots into the wet mixture until evenly distributed.
Fold the dry ingredients into the wet ingredients just until no dry flour remains; do not overmix.
Pour into greased dish (or divide the batter evenly between the prepared pans) and smooth the top(s)
Bake for 25–30 minutes, or until a toothpick inserted in the center comes out clean.
Cool cake in the pan(s) for 10 minutes, then transfer to a wire rack and cool completely before frosting.
To make the frosting, beat the softened cream cheese and butter together until smooth and creamy.
Add the powdered sugar gradually, mixing until combined, then stir in the vanilla until smooth.
Frost the cooled cake (or layers and assemble). Chill briefly if needed to set the frosting.
Garnish top with lemon zest and serve!
Notes
Flavor improves overnight. Store covered in the refrigerator up to 4 days.