Preheat the oven to 350ºF and grease a 9-inch pan, or 2 6-inch pans. I like to add a square of parchment paper to the bottom of the pan, to ensure that my cake will come out later.
In a large bowl, combine the almond flour, eggs, arrowroot starch, maple syrup, baking powder, vanilla, and salt. Stir well until the batter is smooth and no lumps remain, then add in the coconut oil and stir again until very smooth.
Pour the batter into the prepared pan(s) and smooth the top with a spatula. Bake at 350ºF until the top is golden and the center of the cake is firm to the touch, about 30 to 35 minutes.
Let the pan cool in the pan for 15 minutes. then run a knife around the edge of the pan and flip it over on to a plate to release the cake. Let it cool completely before frosting and serving.
I have only tested this version with blanched almond flour, so I can't say how substitutes may affect it. My guess is that almond meal will produce a denser, less fluffy cake.