-
1
Position a rack in the middle of the oven and preheat to 350 degrees Fahrenheit.
-
2
Butter two 9-by-2-inch round cake pans.
-
3
Line the bottoms of the pans with a circle of parchment paper.
-
4
Lightly butter the parchment and dust with flour; tap the side of the pans on the countertop to dislodge any excess flour.
-
5
Whisk the cocoa powder into the boiling water until smooth.
-
6
Add the buttermilk and vanilla and whisk to combine.
-
7
Onto a piece of parchment, sift together the measured flour, baking soda, salt, ancho chile powder, and, if using, cayenne.
-
8
In the bowl of a stand mixer fitted with the paddle attachment, beat the measured butter with the white and brown sugars on medium speed until light and fluffy.
-
9
Add the eggs 1 at a time, beating well after each addition.
-
10
Scrape down the sides of the bowl a few times while beating.
-
11
On low speed, add half the dry ingredients, all of the cocoa mixture, and the remaining dry ingredients, beating after each addition until combined.
-
12
Divide the batter between the prepared pans (you can make sure theyre divided evenly by using a scale to weigh them).
-
13
Bake until a toothpick inserted into the center of the cakes comes out clean, about 25 minutes.
-
14
Let cool in the pans on wire racks for about 10 minutes, then invert the cakes onto the racks, peel off the parchment, and let cool before frosting.
