Whisk together the dry ingredients in a large bowl.
Add the wet ingredients to the dry, and whisk to combine.
Transfer the batter to a prepared cake pan.
Bake until a toothpick inserted in the center comes out clean, about 35 to 45 minutes at 350F.
Make the chocolate frosting once the cake is cooled.
Transfer the cooled cake to a serving platter and frost with the buttercream.