• Preheat oven to 350F. Grease two 8-inch round cake pans (with at least 2" depth to the sides) and line bottoms with a round of parchment paper.
• In a large bowl whisk together the oil and eggs, then whisk in the sugars until there are no lumps.
• Whisk in the vanilla, cinnamon, nutmeg, and salt and baking soda.
• Fold in the flour, and after a few turns, add the walnuts and zucchini and gently fold until everything is well incorporated and evenly distributed, but you don't want to over mix at this point.
• Divide the batter between your 2 prepared pans. Bake for 35-40 minutes until the tops spring back when lightly touched, and a toothpick inserted in the center comes out without wet batter on it, moist crumbs are fine.
• Let the layers cool in the pans for 15 minutes, then loosen the sides with a thin offset spatula and invert onto a cooling rack to finish cooling completely before frosting.

to make the frosting

• Cream the butter and cream cheese together. I do this in my food processor, fitted with the metal blade, but you can do it in a stand mixer or with electric beaters. Blend in the lemon juice, vanilla, and salt.
• Blend in the sugar, one cup at a time. Scrape down the sides of the bowl as necessary.
• Frost the cooled cake. Top with crushed walnuts.