Bring the beef tenderloin to room temperature by allowing it to sit on the counter for at least 30 minutes before cooking.
In a small bowl, stir together the softened butter, grated garlic, rosemary, salt, pepper, thyme, and sage.
Pat the beef tenderloin dry with a paper towel and then rub the compound butter evenly over every side.
Place the beef tenderloin in the air fryer and cook it at 400 degrees F for 5 minutes.
Reduce the heat to 350 degrees F and continue to cook the tenderloin for another 12-15 minutes, or until the internal temperature of the beef reaches 120 degrees F with an instant-read thermometer.
Cover the beef tenderloin with foil and allow it to rest for 10 minutes before slicing.
Serve the beef tenderloin with your favorite sides and enjoy immediately.
Store any leftovers in an airtight container in the fridge for up to three days.
Notes
Check with your butcher to see if they can tie your beef tenderloin.
Don't overcook your tenderloin. It is meant to be served with a pink center.