Remove the 2-pound tri-tip from its packaging, rinse briefly if desired, and pat dry thoroughly with paper towels.
Rub 4 teaspoons olive oil evenly over the entire surface of the tri-tip.
In a small bowl, combine 2 teaspoons salt, 1/2 teaspoon dried oregano, 2 teaspoons garlic powder, 1 1/2 teaspoons onion powder, 1 teaspoon black pepper, 1/2 teaspoon paprika, and 1 pinch cayenne pepper (optional). Mix until uniform.
Rub the spice mixture evenly over both sides of the tri-tip, pressing gently so the seasoning adheres.
Let the seasoned tri-tip rest at room temperature for 30 minutes to absorb the flavors.
Preheat the air fryer to 400°F. Place the tri-tip in the air fryer basket in a single layer (fat cap up or down as you prefer).
Cook for 12–18 minutes, flipping once halfway through if you wish. Start checking the internal temperature with an instant-read meat thermometer toward the lower end of the time range.
Remove the tri-tip when it reaches your desired internal temperature (for reference: about 125°F rare, 135°F medium-rare, 145°F medium).
Transfer the tri-tip to a cutting board and let it rest 5–10 minutes before slicing. Slice against the grain and serve.