Prep the air fryer: Preheat to 320°F (160°C) for 3–5 minutes. Line the basket or tray with parchment or place silicone cupcake molds inside. Use sturdy, oven-safe liners or silicone cups so they hold their shape.

Mix dry ingredients: In a medium bowl, whisk flour, sugar, baking powder, and salt until evenly combined. This prevents clumps and ensures a tender crumb.

Combine wet ingredients: In a separate bowl, whisk oil, melted butter, milk, egg, and vanilla until smooth. The mix should look glossy and uniform.

Make the batter: Pour the wet mixture into the dry. Stir gently with a spatula until just combined. Do not overmix; a few small streaks of flour are fine. Fold in any add-ins.

Fill the liners: Divide the batter among 8–10 cupcake liners, filling each about 2/3 full. Avoid overfilling, which can cause overflow and uneven tops.

Arrange in the basket: Place 4–6 cupcakes in the air fryer at a time, ensuring space between them for airflow. Bake in batches if needed.

Bake: Cook at 320°F (160°C) for 10–12 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs. Start checking at 9 minutes; air fryers vary.

Cool: Let cupcakes sit in the cups for 3 minutes, then transfer to a wire rack to cool completely before frosting. This prevents soggy bottoms and melting frosting.

Make the frosting: Beat softened butter until creamy. Add powdered sugar, salt, vanilla, and 1 tbsp milk. Beat on medium until fluffy, adding more milk as needed to reach a spreadable consistency.

Frost and decorate: Spread or pipe the buttercream onto cooled cupcakes. Add sprinkles, zest curls, or a drizzle of melted chocolate if you like.