Preheat oven to 350 degrees F.  Oil a round 8 or 9 inch cake pan and line the bottom with parchment.

Make the cake.  In a large bowl, stir together the flour, sugar, baking powder and soda, ginger, and lemon zest until combined.  Stir in the oil, followed by the eggs until a thick batter forms.  Stir in the zucchini and walnuts.

Pour into the prepared pan and bake 45-55 minutes until a toothpick inserted in the center comes out clean or with a few moist crumbs.  Cool completely in the pan.

Once the cake is cool, make the frosting.  Melt the coconut butter in a microwave safe bowl in the microwave in 20 second increments, stirring in between, until fully melted.  Stir in the syrup, milk, cinnamon, and salt until combined.  Add more milk as necessary until the frosting comes together and is spreadable.  Spread onto the cake, allow to set about 20 minutes, and serve.

Cake may be stored in an airtight container at room temperature for up to 4 days or in the freezer, wrapped in parchment and foil and placed in a zipper bag for up to 3 months.  Thaw in the microwave about 1 minute or at room temperature about 2 hours.