In a medium bowl, combine olive oil and brown sugar until combined.
Add pumpkin seeds, salt, and cinnamon. Stir until seeds are evenly coated.
Spread seeds in a single layer in the air fryer basket (use a liner if preferred).
Cook for 8-10 minutes, shaking halfway through, until seeds are crisp.
Cool completely before serving.
Notes
The seeds will continue to toast slightly even after the cooking time is finished. Allow them to cool before serving.
For clustered pumpkin seeds, dissolve the brown sugar first in the microwave or on the stovetop. You can also replace brown sugar with honey or maple syrup.