Prepare the Pecan Mixture: In a large mixing bowl, combine the olive oil, brown sugar, ground cinnamon, cayenne pepper, salt, vanilla extract, and water. If you're using fresh rosemary, add it here as well. Mix until the ingredients form a smooth paste.
Coat the Pecans: Add the pecan halves to the mixing bowl and stir until all pecans are evenly coated with the spiced mixture.
Preheat the Air Fryer: Preheat your air fryer to 350°F (175°C) for about 4.0 minutes.
Air Fry the Pecans: Place the coated pecans in one even layer in the air fryer basket. Avoid overcrowding to ensure even cooking.
Cook: Air fry the pecans for about 7.0 minutes, shaking the basket halfway through to ensure they cook evenly. Keep an eye on them to prevent burning.
Cool the Pecans: Once they are golden brown and fragrant, remove the basket from the air fryer and let the pecans cool on a baking sheet lined with parchment paper.
Serve or Store: Enjoy immediately as a snack or store in an airtight container at room temperature for up to two weeks.
Notes
Adjust cayenne pepper to taste for desired spice level.