Spray two 9″ cake pans lightly with cooking oil spray. Use round pieces of parchment paper, or cut round pieces, and place them in the bottoms of the pans. Hit the paper lightly with a little more spray.
Measure two cups of all-purpose flour or weigh 260 grams.
Add two cups of granulated sugar, or re-zero the scale and weigh 396 grams.
Add half an eight-ounce package of cocoa powder, or measure 3/4 cup, or re-zero the scale and weigh 4 ounces.
Add the baking powder, baking soda, salt, and (optional) espresso powder.
Stir on low speed until the dry ingredients are combined and it all looks the same color. Add the buttermilk, vegetable oil, eggs, and vanilla, and mix on medium speed until blended.
Stop the mixer, carefully pour in the boiling water, stand back in case there are splashes, and start the mixer on its lowest speed. After all the water is mixed in, you can speed it up a little until the boiling water is blended. The batter will be very thin.
After you remove the bowl from the mixer, there will be heavier batter at the bottom of the bowl that the paddle missed. Be sure to blend that in with your spatula before you continue.
Pour the batter into the two prepared cake pans and place in the oven, a little back of the center, away from the door.
It’s a good idea to weigh the two pans, and spoon a little batter from one to the other, until they are the same weight, so they get done at the same time.
Bake for 30 to 35 minutes.
The cake is done when a toothpick inserted deeply into the center comes out clean. If not, add time in increments of at least two minutes so the oven will stay hot.
Take the finished cakes out of the oven and let them cool for about ten minutes until they’re safe to touch.
Use the dull side of a table knife to be sure the cake isn’t stuck to the sides of the pan.
Put a wire rack on top of each cake pan, invert the cake, pan, and wire rack together, thump the bottom of the pan hard once to free the cake, and then remove the cake pan and the parchment paper.
Put four small pieces of wax paper under the cake from four sides so the frosting won’t get beyond the cake.
Place the bottom layer flat side down, and scoop enough frosting on top to fill the space between the layers. Center the top layer flat side down over the bottom layer. Use the top layer to press down on the frosting.
Scoop the remaining frosting onto the top of the cake and spread it out with your spatula.
Use a table knife to bring gobs of frosting from the top and spread it out on the sides. Turn the cake against the knife to even out the sides.
Spread the frosting on top until it’s level and remove the wax paper.
Cake decorating is another whole topic that we don’t cover here. Have fun!