Lightly grease two 8-inch pans with at least 2-inch sides with coconut oil and line with parchment paper rounds. Set aside.

In a medium bowl, whisk together the oat flour, sugars, cocoa powder, baking soda, baking powder, and salt.

In a large bowl, whisk together the coconut oil, eggs, buttermilk, and vanilla. Stir and whisk the dry ingredients into the wet ingredients and stir very well to combine. Stir in the coffee and stir until batter is smooth and combined.

Pour batter evenly into prepared pans and preheat oven to 350 F. Let batter rest while the oven heats, about 15 minutes.

Place pans in the oven and bake for 45-50 minutes, checking at 45 minutes, until a toothpick in the center comes out clean and the edges are starting to pull away from the edges of the pans. Remove from oven and let cake cool in the pans on a wire rack for 30 minutes, then turn out onto the rack to cool fully. The cake will be quite tender and soft - yum! - so it's a good idea to refrigerate it before frosting or do a crumb coat.

Frost cake with or your frosting of choice, either as a layer cake or frost one layer and freeze the other for another time (what I did on the second recipe test). Cake will keep well wrapped in the fridge for up to 5 days.