Preheat Air Fryer to 330 degrees F. Spray brownie pan with nonstick cooking spray.
In medium bowl, stir together melted butter and sugar. Add egg and vanilla and mix well. Add dry ingredients and stir just until combined.
Spread batter into prepared pan. Place pan in Air Fryer basket and set timer for 13 minutes. Use toothpick to check for doneness. Cook another 2-3 minutes if needed.
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