Prep the pan and air fryer: Lightly grease a 6-inch cake pan and line the bottom with parchment. Spray again. Preheat your air fryer to 320°F (160°C) for 3–5 minutes if your unit requires preheating.

Combine dry ingredients: In a medium bowl, whisk flour, sugar, cocoa powder, baking soda, and salt until no cocoa clumps remain.

Mix wet ingredients: In a separate bowl, whisk buttermilk, oil, egg, vanilla, vinegar, and red gel food coloring. Start with 1 teaspoon coloring, then add more to reach a deep red hue.

Make the batter: Pour the wet mixture into the dry. Whisk just until combined and smooth. Do not overmix—stop when you no longer see dry streaks.

Fill the pan: Scrape batter into the prepared pan and smooth the top. Tap the pan on the counter twice to release air bubbles.

Air fry: Place the pan in the air fryer basket. Cook at 320°F (160°C) for 22–28 minutes, rotating the pan halfway if your air fryer has hot spots. It’s done when a toothpick comes out with a few moist crumbs, not wet batter.

Cool: Let the cake cool in the pan for 10 minutes. Run a thin knife around the edge, then turn onto a rack. Peel off parchment and cool completely, about 45–60 minutes.

Make the frosting: Beat cream cheese and butter until smooth. Add powdered sugar, vanilla, and a pinch of salt. Beat until fluffy, 1–2 minutes. Adjust thickness with a teaspoon of milk if needed, or add more powdered sugar for a stiffer frosting.

Frost and serve: Once the cake is fully cool, spread frosting on top and down the sides. For a simple finish, keep it as a single layer. Slice and enjoy.