Preheat your oven to 350°F (175°C). Grease your 9x13-inch baking dish with a little melted coconut oil or butter to prevent sticking.
In a large mixing bowl, combine the sifted coconut flour, arrowroot flour, baking powder, and sea salt. Whisk together until well blended, ensuring there are no lumps.
In another bowl, beat the eggs until fluffy. Add in the pure maple syrup, full-fat canned coconut milk, and melted butter. Whisk until the mixture is smooth and creamy.
Pour the wet ingredients into the dry ingredients. Use a spatula to gently fold everything together until just combined. Be careful not to overmix.
Fold in the chopped walnuts and ground cinnamon, ensuring they are evenly distributed throughout the batter.
Pour the batter into the prepared baking dish and spread it out evenly with your spatula.
Place the baking dish in the preheated oven. Bake for 30-35 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
While the cake is baking, mix the remaining 2 tablespoons of pure maple syrup with a pinch of salt in a small bowl. This will be drizzled over the cake once it’s out of the oven.
Once baked, remove the cake from the oven and let it cool for about 10 minutes. Drizzle the maple syrup mixture over the top, slice, and enjoy!