Preheat oven to 350°F (175°C). Grease and flour a 9x13-inch baking pan.
In a medium bowl, stir together flour, baking powder, baking soda, cinnamon, and nutmeg. Set aside.
In a large bowl, cream together butter and sugar until light and fluffy. Beat in eggs one at a time, then stir in vanilla. Gradually stir in the dry ingredients until just blended. Fold in zucchini and walnuts (if desired). Spread evenly into the prepared pan.
Bake for 40 to 45 minutes, or until a toothpick inserted into the center of the cake comes out clean. Let cool in the pan for 10 minutes, then turn out onto a wire rack and cool completely.
Interesting Facts
Zucchini cake is a great way to use up all that extra zucchini you have on hand.
The addition of walnuts is optional, but they add a nice flavor and crunch to the cake.