Line an 8x8 baking dish (or equally sized pan) with parchment paper letting the edges hang over the sides of the pan.
By hand or with a food processor using the grating attachment, shred the carrots. Place them in a large bowl and set aside. Clean out the food processor and switch to the blade attachment. Blend together the walnuts and dates into a uniform crumb; it should sticks together when pressed between your fingers. Add carrots, coconut, spices, and salt and blend again, scraping down the sides as needed, until the carrots are fully incorporated.
Press the cake into the prepared pan, smooth over the top, and place in the freezer while making the cream cheese frosting.
To make the cream cheese frosting, combine cashews, water, agave nectar or maple syrup, vanilla, salt, and lemon juice in a high-powered blender. Blend until silky smooth. Add coconut oil and blend to combine. Pour onto the chilled cake and smooth the top. Cover in plastic wrap and freeze for at least 2 hours.
When ready to serve, remove the cake from the freezer. To release it from the pan, pull up the sides of the parchment paper. Top with walnuts and dust with cinnamon. Let it thaw 10 minutes at room temperature.
With a hot, sharp knife cut cake into 2 x 2-inch pieces. If the cake is very frozen, let it thaw an additional 15 minutes before serving.