Preheat the oven to 350 degrees F and line an 8 inch cake pan with parchment paper.
Place the cup of grated zucchini into a bowl and add the brown sugar, eggs, oil, milk and vanilla. Mix well with a fork.
Using a sieve, add the cocoa powder, sorghum, rice flour, baking powder and salt and mix until lump free.
Pour the batter into the prepared cake pan and bake for 45 minutes and the center is no longer soft. Let cool.
Make the frosting by combining the cream cheese, butter, powdered sugar, matcha and salt in the bowl of a stand mixer.
Beat until light and fluffy making sure to scrape the sides of the bowl a few times.
Once the cake is cool, spread the frosting all over the top. Serve at room temperature or store in the fridge until needed remembering to bring back to room temp.