Instructions

1. Arrange a rack in the middle of the oven and heat the oven to 350°F. Coat a 9x13-inch baking pan with cooking spray. Dust the pan with all-purpose flour, tapping out the excess.
2. Place 4 large eggs in the bowl of a stand mixer (or large bowl if using an electric hand mixer). Beat with the paddle attachment on low speed until combined, about 30 seconds. Add 2 cups granulated sugar and beat on low speed until combined, about 1 minute. Add 1 1/2 cups neutral oil and beat on low speed until combined, about 1 minute.
3. Place 3 cups all-purpose flour, 2 tablespoons plus 1 12 teaspoons baking powder, 2 teaspoons baking soda, 1 1/2 teaspoons ground cinnamon, and 1 1/2 teaspoons kosher salt in a medium bowl and whisk to combine.
4. Add half of the flour mixture to the egg mixture and fold with a flexible spatula until just combined. Add 16 ounces carrot baby food and fold until just combined. Add the remaining flour mixture and fold until just combined. Add 3/4 cup chopped walnuts if using and 1 teaspoon vanilla extract and fold until just combined. Transfer to the baking pan and spread into an even layer.
5. Bake until a tester inserted into the center of the cake comes out clean, 45 to 60 minutes.
6. When the cake is ready, place the pan on a wire rack and let cool completely, about 2 hours. Meanwhile, place 6 ounces cream cheese in the clean, dry bowl of the stand mixer (or large bowl if using an electric hand mixer). Let sit at room temperature to soften.
7. Beat the cream cheese with the paddle attachment on medium speed until fluffy, about 3 minutes.
8. Add 2 tablespoons whole milk and 1 teaspoon vanilla extract and beat until combined, about 30 seconds. Add 2 cups powdered sugar and beat until smooth and combined, about 1 minute. If the icing is thin, beat in more powdered sugar a tablespoon at a time as needed.
9. Spread the icing onto the cooled cake in an even layer. Garnish with more chopped walnuts if desired.