Preheat oven to 350 degrees F. Lightly grease an 8 inch round cake pan with cooking spray and set aside.
In a small bowl, whisk together coconut milk, coconut oil, vanilla extract, vinegar, and pumpkin until combined. Set aside.
In a medium sized mixing bowl whisk together the flours, erythritol, cinnamon, and baking soda until no lumps remain.
Pour the wet mixture into the dry and stir to combine. The batter will be very thick and look more like dough than typical batter. I suggest mixing everything together with your hands instead to make sure it gets evenly incorporated. Once everything is mostly combined, pour in pecans and continue mixing with your hands so they are evenly distributed.
Once fully combined transfer the batter/dough to your prepared cake tin and press it down evenly in the pan.
Bake for 25 minutes or until the edges are golden brown. The cake will continue cooking once removed from the oven!