In a large mixing bowl, mix the flour, baking powder, baking soda, and salt.
Then add the buttermilk and milk. Add in the melted butter, sugar, egg, and vanilla extract, mix well
Grease the donut pan with olive oil spray, and then fill the cavity about 2/3 the way full with the batter.
In another bowl, mix the topping, brown sugar, ground cinnamon, salt, butter, and flour, mix until crumbly.
Sprinkle the topping onto the base batter. Set the donut pan into the air fryer at 320 degrees F for 12 minutes.
Plate, serve, and enjoy!