Preheat the air fryer to 400℉.
In a large bowl, whisk together the flour, baking soda, baking powder and salt, set aside.
In another bowl whisk melted butter, oil and egg. Add the buttermilk, banana, vanilla and sugar. Add the wet ingredients to the dry and stir just to combine.
Fold in the nuts.
Scoop muffin mix into seven silicone muffin liners and place in the air fryer. (My air fryer is large enough to accommodate a 9-inch cake pan. I place the silicone liners in the pan and then place in the air fryer with tongs and remove with tongs.)
Bake at 400℉ for 4 minutes. Lower temperature to 325℉ and bake an additional 11 - 13 minutes.
Remove from air fryer and cool to touch.
