Step 1

Preheat oven to 350 degrees.

Step 2

Grease two 9-inch round cake pans.

Step 3

Cream together sugar and oil in a large bowl.

Step 4

Add grated zucchini and eggs and mix together well.

Step 5

Add the dry ingredients - flour, baking powder, baking soda, salt, and cinnamon. Mix to combine.

Step 6

Divide cake batter equally into the cake pans.

Step 7

Bake at 350 degrees for 35 to 40 minutes or until a toothpick inserted in the center comes out clean.

Step 8

Remove the cake from the pans and place them on wire racks. Cool completely before frosting.

Step 9

Cool the walnuts completely.

Step 10

Allow butter and cream cheese to soften at room temperature.

Step 11

Using an electric mixer, beat cream cheese and butter together in a large bowl until thoroughly combined and smooth.

Step 12

Slowly add in powdered sugar while mixing on low speed.

Step 13

Add vanilla extract and mix it into the frosting.

Step 14

Place one cake layer on a cake plate or cake stand.

Step 15

Spread frosting on top of the cake layer.

Step 16

Place the second cake layer on top.

Step 17

Spread frosting on the top and sides of the cake.

Step 18

Lightly toast the black walnuts in the oven at 350 degrees for 8 minutes.

Step 19

Chop the walnuts if they are not already chopped. Cool completely.

Step 20

Sprinkle walnuts on top of the cake.