Step 1

Wrap a 6-inch (15cm) cake pan with a baking pan strip or a foil strip with a damp paper towel inside. Also, line the inside of the pan with parchment paper. The easiest way is to cut a circle out of parchment paper for the bottom and strips for the sides. Set aside.

Step 2

Preheat the air fryer to 320°F (160°C).

Step 3

In a large bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt and set aside.

Step 4

In another large mixing bowl, whisk together the egg, oil, buttermilk, and vanilla. Add the sugar and whisk until frothy for 1 minute. Add the flour mixture and whisk just to combine. Gradually add the hot water as you whisk, and whisk just to combine. Be careful not to burn yourself. The batter will be thin.

Step 5

Pour the batter into the prepared cake pan and cover with aluminum foil. Pierce a few times to allow the steam to escape while baking. Bake for 45 minutes, then remove the foil and bake uncovered for another 5 minutes if necessary. The cake is done when a toothpick inserted into the center comes out clean with a few moist crumbs.

Step 6

Let cool in the pan for 15 minutes. Then remove from the pan, transfer to a cooling rack, and let cool completely. Fill and decorate to your liking or serve as is. Store in an airtight container at room temperature for up to 4 days.