Preheat the oven to 350° Fahrenheit and grease two 9-inch round cake pans and set aside. Make the cakes! In a medium bowl, whisk together the gluten free flour, almond meal, baking powder and soda, salt, and cinnamon. Then, in a large bowl, whisk together the oil, melted butter, eggs, sour cream, vanilla, sugar, and brown sugar. Dump the dry ingredients into the wet, and stir together until combined. Scoop 2-3 large spoonfuls of batter into each cake pan and shake until the entire bottom of the pan is covered in a thin layer of cake bater.
Then, make the cake swirl. Melt the butter and stir together the butter, brown sugar, cocoa powder, and cinnamon until thick and combined. Then, spoon teaspoonfuls of the swirl mixture on top of the cake batter in each pan until all of the swirl mixture has been used. Pour the remaining cake batter on top of the swirl mixture evenly in each pan and then use a small spoon to swirl the swirl into the batter (or leave as a layer). Bake for 30 minutes or until a knife inserted into the center of the cake comes out clean. Let cool completely before turning out and constructing the cake.
While the cake is cooling, make the buttercream! First, melt the dark baking chocolate and then let it cool to room temp (I put it in the fridge for about 10 minutes, taking it out to stir it every couple of minutes). While the chocolate is cooling, in a large bowl, using an electric mixer, beat together the room temp butter and one cup of the powdered sugar until thick and creamy. Add in the remaining powdered sugar one cup at a time and beat until smooth. Add in the cocoa powder, cinnamon, and vanilla extract and beat until smooth. Add in the cooled melted chocolate (if it's still warm, wait until it's cool or it will melt the butter in the buttercream) and the cocoa powder. Beat the chocolate and cocoa powder into the buttercream until combined.
Now for the fun part - add in about a 1/4 of a teaspoon of the cayenne and the ancho chili powder at a time and beat to combine, tasting the buttercream after each addition until you reach your favorite spicy point. I added the full teaspoon of each (the butter dulls the spiciness), but you can add more or less depending on your taste.
Once you've finished making the buttercream, turn out each cake layer, top up, onto a baking sheet. Use a long knife to carefully cut off the rounded top of each cake layer, so that each layer is perfectly flat (optional, but makes constructing the cake easier). Then, place one layer on your plate or serving platter. Use a butter knife or frosting knife to frost the layer (generously - about 1/2 an inch of frosting evenly across the layer). Then place the second layer on top, and add more frosting to the tops and sides (optional, you can just frost the top or you can continue to frost the sides of the cake). Dust with cinnamon and then serve!