In a large mixing bowl, mix the flour, sugar, baking powder, and salt. Mix well.
In another mixing bowl, mix the oil, egg, vanilla extract, and buttermilk.
Then mix the wet ingredients into the dry ingredients, mix well.
Fold in the FROZEN blueberries, mix well.
Spray your muffin tin with cooking spray or line with muffin liners.
Spoon the batter into the muffin cavity, filling about 2/3 way full.
Spoon a couple of tablespoons of topping on each muffin.
Set the muffin tin into the air fryer basket, set the temperature to 320 degrees F for 12-15 minutes.
Let slightly cool before serving.